workqueue: skip the node_nr_active update for non-unbound workqueuesgrafted

apply_wqattrs_commit() updates node_nr_active->max unconditionally.
wq->node_nr_active[] is only allocated for unbound workqueues, so guard
the call before per-cpu workqueues start using this path.

No functional change: only unbound workqueues reach apply_wqattrs_*()
today.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

5 files changed, 674 insertions, 0 deletions

diff --git a/Documentation/firmware-guide/acpi/dsd/data-node-references.rst b/Documentation/firmware-guide/acpi/dsd/data-node-references.rst
new file mode 100644
index 000000000..ccb4b153e
--- /dev/null
+++ b/Documentation/firmware-guide/acpi/dsd/data-node-references.rst
@@ -0,0 +1,94 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+===================================
+Referencing hierarchical data nodes
+===================================
+
+:Copyright: |copy| 2018, 2021 Intel Corporation
+:Author: Sakari Ailus <sakari.ailus@linux.intel.com>
+
+ACPI in general allows referring to device objects in the tree only.
+Hierarchical data extension nodes may not be referred to directly, hence this
+document defines a scheme to implement such references.
+
+A reference to a _DSD hierarchical data node is a string consisting of a
+device object reference followed by a dot (".") and a relative path to a data
+node object. Do not use non-string references as this will produce a copy of
+the hierarchical data node, not a reference!
+
+The hierarchical data extension node which is referred to shall be located
+directly under its parent object i.e. either the device object or another
+hierarchical data extension node [dsd-guide].
+
+The keys in the hierarchical data nodes shall consist of the name of the node,
+"@" character and the number of the node in hexadecimal notation (without pre-
+or postfixes). The same ACPI object shall include the _DSD property extension
+with a property "reg" that shall have the same numerical value as the number of
+the node.
+
+In case a hierarchical data extensions node has no numerical value, then the
+"reg" property shall be omitted from the ACPI object's _DSD properties and the
+"@" character and the number shall be omitted from the hierarchical data
+extension key.
+
+
+Example
+=======
+
+In the ASL snippet below, the "reference" _DSD property contains a string
+reference to a hierarchical data extension node ANOD under DEV0 under the parent
+of DEV1. ANOD is also the final target node of the reference.
+::
+
+	Device (DEV0)
+	{
+	    Name (_DSD, Package () {
+		ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+		Package () {
+		    Package () { "node@0", "NOD0" },
+		    Package () { "node@1", "NOD1" },
+		}
+	    })
+	    Name (NOD0, Package() {
+		ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		Package () {
+		    Package () { "reg", 0 },
+		    Package () { "random-property", 3 },
+		}
+	    })
+	    Name (NOD1, Package() {
+		ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+		Package () {
+		    Package () { "reg", 1 },
+		    Package () { "anothernode", "ANOD" },
+		}
+	    })
+	    Name (ANOD, Package() {
+		ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		Package () {
+		    Package () { "random-property", 0 },
+		}
+	    })
+	}
+
+	Device (DEV1)
+	{
+	    Name (_DSD, Package () {
+		ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		Package () {
+		    Package () { "reference", "^DEV0.ANOD" }
+		    },
+		}
+	    })
+	}
+
+Please also see a graph example in
+Documentation/firmware-guide/acpi/dsd/graph.rst.
+
+References
+==========
+
+[dsd-guide] DSD Guide.
+    https://github.com/UEFI/DSD-Guide/blob/main/dsd-guide.adoc, referenced
+    2021-11-30.
diff --git a/Documentation/firmware-guide/acpi/dsd/graph.rst b/Documentation/firmware-guide/acpi/dsd/graph.rst
new file mode 100644
index 000000000..d6ae5ffa7
--- /dev/null
+++ b/Documentation/firmware-guide/acpi/dsd/graph.rst
@@ -0,0 +1,170 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======
+Graphs
+======
+
+_DSD
+====
+
+_DSD (Device Specific Data) [dsd-guide] is a predefined ACPI device
+configuration object that can be used to convey information on
+hardware features which are not specifically covered by the ACPI
+specification [acpi]. There are two _DSD extensions that are relevant
+for graphs: property [dsd-guide] and hierarchical data extensions. The
+property extension provides generic key-value pairs whereas the
+hierarchical data extension supports nodes with references to other
+nodes, forming a tree. The nodes in the tree may contain properties as
+defined by the property extension. The two extensions together provide
+a tree-like structure with zero or more properties (key-value pairs)
+in each node of the tree.
+
+The data structure may be accessed at runtime by using the device_*
+and fwnode_* functions defined in include/linux/fwnode.h .
+
+Fwnode represents a generic firmware node object. It is independent on
+the firmware type. In ACPI, fwnodes are _DSD hierarchical data
+extensions objects. A device's _DSD object is represented by an
+fwnode.
+
+The data structure may be referenced to elsewhere in the ACPI tables
+by using a hard reference to the device itself and an index to the
+hierarchical data extension array on each depth.
+
+
+Ports and endpoints
+===================
+
+The port and endpoint concepts are very similar to those in Devicetree
+[devicetree, graph-bindings]. A port represents an interface in a device, and
+an endpoint represents a connection to that interface. Also see [data-node-ref]
+for generic data node references.
+
+All port nodes are located under the device's "_DSD" node in the hierarchical
+data extension tree. The data extension related to each port node must begin
+with "port" and must be followed by the "@" character and the number of the
+port as its key. The target object it refers to should be called "PRTX", where
+"X" is the number of the port. An example of such a package would be::
+
+    Package() { "port@4", "PRT4" }
+
+Further on, endpoints are located under the port nodes. The hierarchical
+data extension key of the endpoint nodes must begin with
+"endpoint" and must be followed by the "@" character and the number of the
+endpoint. The object it refers to should be called "EPXY", where "X" is the
+number of the port and "Y" is the number of the endpoint. An example of such a
+package would be::
+
+    Package() { "endpoint@0", "EP40" }
+
+Each port node contains a property extension key "port", the value of which is
+the number of the port. Each endpoint is similarly numbered with a property
+extension key "reg", the value of which is the number of the endpoint. Port
+numbers must be unique within a device and endpoint numbers must be unique
+within a port. If a device object may only has a single port, then the number
+of that port shall be zero. Similarly, if a port may only have a single
+endpoint, the number of that endpoint shall be zero.
+
+The endpoint reference uses property extension with "remote-endpoint" property
+name followed by a string reference in the same package. [data-node-ref]::
+
+    "device.datanode"
+
+In the above example, "X" is the number of the port and "Y" is the number of
+the endpoint.
+
+The references to endpoints must be always done both ways, to the
+remote endpoint and back from the referred remote endpoint node.
+
+A simple example of this is show below::
+
+    Scope (\_SB.PCI0.I2C2)
+    {
+	Device (CAM0)
+	{
+	    Name (_DSD, Package () {
+		ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		Package () {
+		    Package () { "compatible", Package () { "nokia,smia" } },
+		},
+		ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+		Package () {
+		    Package () { "port@0", "PRT0" },
+		}
+	    })
+	    Name (PRT0, Package() {
+		ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		Package () {
+		    Package () { "reg", 0 },
+		},
+		ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+		Package () {
+		    Package () { "endpoint@0", "EP00" },
+		}
+	    })
+	    Name (EP00, Package() {
+		ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		Package () {
+		    Package () { "reg", 0 },
+		    Package () { "remote-endpoint", "\\_SB.PCI0.ISP.EP40" },
+		}
+	    })
+	}
+    }
+
+    Scope (\_SB.PCI0)
+    {
+	Device (ISP)
+	{
+	    Name (_DSD, Package () {
+		ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+		Package () {
+		    Package () { "port@4", "PRT4" },
+		}
+	    })
+
+	    Name (PRT4, Package() {
+		ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		Package () {
+		    Package () { "reg", 4 }, /* CSI-2 port number */
+		},
+		ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+		Package () {
+		    Package () { "endpoint@0", "EP40" },
+		}
+	    })
+
+	    Name (EP40, Package() {
+		ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		Package () {
+		    Package () { "reg", 0 },
+		    Package () { "remote-endpoint", "\\_SB.PCI0.I2C2.CAM0.EP00" },
+		}
+	    })
+	}
+    }
+
+Here, the port 0 of the "CAM0" device is connected to the port 4 of
+the "ISP" device and vice versa.
+
+
+References
+==========
+
+[acpi] Advanced Configuration and Power Interface Specification.
+    https://uefi.org/specifications/ACPI/6.4/, referenced 2021-11-30.
+
+[data-node-ref] Documentation/firmware-guide/acpi/dsd/data-node-references.rst
+
+[devicetree] Devicetree. https://www.devicetree.org, referenced 2016-10-03.
+
+[dsd-guide] DSD Guide.
+    https://github.com/UEFI/DSD-Guide/blob/main/dsd-guide.adoc, referenced
+    2021-11-30.
+
+[dsd-rules] _DSD Device Properties Usage Rules.
+    Documentation/firmware-guide/acpi/DSD-properties-rules.rst
+
+[graph-bindings] Common bindings for device graphs (Devicetree).
+    https://github.com/devicetree-org/dt-schema/blob/main/schemas/graph.yaml,
+    referenced 2021-11-30.
diff --git a/Documentation/firmware-guide/acpi/dsd/leds.rst b/Documentation/firmware-guide/acpi/dsd/leds.rst
new file mode 100644
index 000000000..a97cd07d4
--- /dev/null
+++ b/Documentation/firmware-guide/acpi/dsd/leds.rst
@@ -0,0 +1,102 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+========================================
+Describing and referring to LEDs in ACPI
+========================================
+
+Individual LEDs are described by hierarchical data extension [5] nodes under the
+device node, the LED driver chip. The "reg" property in the LED specific nodes
+tells the numerical ID of each individual LED output to which the LEDs are
+connected. [leds] The hierarchical data nodes are named "led@X", where X is the
+number of the LED output.
+
+Referring to LEDs in Device tree is documented in [video-interfaces], in
+"flash-leds" property documentation. In short, LEDs are directly referred to by
+using phandles.
+
+ACPI allows (as does DT) using integer arguments after the reference. A
+combination of the LED driver device reference and an integer argument,
+referring to the "reg" property of the relevant LED, is used to identify
+individual LEDs. The value of the "reg" property is a contract between the
+firmware and software, it uniquely identifies the LED driver outputs.
+
+Under the LED driver device, The first hierarchical data extension package list
+entry shall contain the string "led@" followed by the number of the LED,
+followed by the referred object name. That object shall be named "LED" followed
+by the number of the LED.
+
+Example
+=======
+
+An ASL example of a camera sensor device and a LED driver device for two LEDs is
+show below. Objects not relevant for LEDs or the references to them have been
+omitted. ::
+
+	Device (LED)
+	{
+		Name (_DSD, Package () {
+			ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+			Package () {
+				Package () { "led@0", LED0 },
+				Package () { "led@1", LED1 },
+			}
+		})
+		Name (LED0, Package () {
+			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+			Package () {
+				Package () { "reg", 0 },
+				Package () { "flash-max-microamp", 1000000 },
+				Package () { "flash-timeout-us", 200000 },
+				Package () { "led-max-microamp", 100000 },
+				Package () { "label", "white:flash" },
+			}
+		})
+		Name (LED1, Package () {
+			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+			Package () {
+				Package () { "reg", 1 },
+				Package () { "led-max-microamp", 10000 },
+				Package () { "label", "red:indicator" },
+			}
+		})
+	}
+
+	Device (SEN)
+	{
+		Name (_DSD, Package () {
+			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+			Package () {
+				Package () {
+					"flash-leds",
+					Package () { "^LED.LED0", "^LED.LED1" },
+				}
+			}
+		})
+	}
+
+where
+::
+
+	LED	LED driver device
+	LED0	First LED
+	LED1	Second LED
+	SEN	Camera sensor device (or another device the LED is related to)
+
+References
+==========
+
+[acpi] Advanced Configuration and Power Interface Specification.
+    https://uefi.org/specifications/ACPI/6.4/, referenced 2021-11-30.
+
+[data-node-ref] Documentation/firmware-guide/acpi/dsd/data-node-references.rst
+
+[devicetree] Devicetree. https://www.devicetree.org, referenced 2019-02-21.
+
+[dsd-guide] DSD Guide.
+    https://github.com/UEFI/DSD-Guide/blob/main/dsd-guide.adoc, referenced
+    2021-11-30.
+
+[leds] Documentation/devicetree/bindings/leds/common.yaml
+
+[video-interfaces] Documentation/devicetree/bindings/media/video-interfaces.yaml
diff --git a/Documentation/firmware-guide/acpi/dsd/motorcomm-yt8xxx-phy.rst b/Documentation/firmware-guide/acpi/dsd/motorcomm-yt8xxx-phy.rst
new file mode 100644
index 000000000..d64a396fa
--- /dev/null
+++ b/Documentation/firmware-guide/acpi/dsd/motorcomm-yt8xxx-phy.rst
@@ -0,0 +1,107 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================================
+Motorcomm yt8xxx PHY properties (_DSD)
+======================================
+
+This document describes ACPI _DSD device properties for Motorcomm yt8xxx
+Ethernet PHYs supported by the in-kernel driver in
+``drivers/net/phy/motorcomm.c``.
+
+The properties are exposed on the PHY device object under the MDIO bus ACPI
+device (the same objects that are registered via
+``fwnode_mdiobus_register_phy()``). MAC-side connection properties such as
+``phy-handle`` and ``phy-mode`` are documented in [acpi-mdio-phy]_.
+
+Property names and semantics are intentionally aligned with the Devicetree
+binding [motorcomm-yt8xxx]_ so that the same driver code path
+(``device_property_*`` on ``&phydev->mdio.dev``) can consume firmware
+described either as Devicetree or ACPI _DSD.
+
+UUID and placement
+==================
+
+Per [acpi-dsd-properties-rules]_ and [acpi-mdio-phy]_, properties must be
+placed in an _DSD package using the standard Device Properties UUID::
+
+	ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301")
+
+Properties
+==========
+
+Unless noted otherwise, integer properties use the same allowed values and
+defaults as [motorcomm-yt8xxx]_.
+
+``rx-internal-delay-ps`` (u32, optional)
+  RGMII RX internal delay in picoseconds. Only meaningful when the link is
+  using RGMII modes with RX internal delay; see [motorcomm-yt8xxx]_.
+
+``tx-internal-delay-ps`` (u32, optional)
+  RGMII TX internal delay in picoseconds. Only meaningful when the link is
+  using RGMII modes with TX internal delay; see [motorcomm-yt8xxx]_.
+
+``motorcomm,clk-out-frequency-hz`` (u32, optional)
+  Clock output frequency on the PHY clock output pin. Allowed values and
+  default are defined in [motorcomm-yt8xxx]_.
+
+``motorcomm,keep-pll-enabled`` (boolean, optional)
+  If true, keep the PLL enabled even when there is no link (useful for using
+  the clock output without an Ethernet link). See [motorcomm-yt8xxx]_.
+
+``motorcomm,auto-sleep-disabled`` (boolean, optional)
+  If true, disable the PHY auto-sleep behavior described in
+  [motorcomm-yt8xxx]_.
+
+``motorcomm,rx-clk-drv-microamp`` (u32, optional)
+  Drive strength for the ``rx_clk`` RGMII pad in microamps. Allowed values
+  depend on the configured RGMII LDO voltage; see [motorcomm-yt8xxx]_.
+
+``motorcomm,rx-data-drv-microamp`` (u32, optional)
+  Drive strength for the ``rx_data`` and ``rx_ctl`` RGMII pads in microamps.
+  See [motorcomm-yt8xxx]_.
+
+``motorcomm,tx-clk-adj-enabled`` (boolean, optional)
+  Enables adjustments related to ``motorcomm,tx-clk-*-inverted`` usage; see
+  [motorcomm-yt8xxx]_.
+
+``motorcomm,tx-clk-10-inverted`` (boolean, optional)
+``motorcomm,tx-clk-100-inverted`` (boolean, optional)
+``motorcomm,tx-clk-1000-inverted`` (boolean, optional)
+  Per-speed TX clock inversion options; see [motorcomm-yt8xxx]_.
+
+ASL example (illustrative)
+==========================
+
+The example below only shows PHY-local _DSD properties. A real platform
+still needs a MAC ``phy-handle`` and ``phy-mode`` package as in
+[acpi-mdio-phy]_.
+
+.. code-block:: none
+
+	Scope (\_SB.MDI0)
+	{
+		Device (PHY4)
+		{
+			Name (_ADR, 0x4)
+
+			Name (_DSD, Package () {
+				ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+				Package () {
+					Package (2) { "rx-internal-delay-ps", 2100 },
+					Package (2) { "tx-internal-delay-ps", 150 },
+					Package (2) { "motorcomm,clk-out-frequency-hz", 0 },
+					Package (2) { "motorcomm,keep-pll-enabled", 1 },
+					Package (2) { "motorcomm,auto-sleep-disabled", 1 },
+				}
+			})
+		}
+	}
+
+References
+==========
+
+.. [acpi-mdio-phy] Documentation/firmware-guide/acpi/dsd/phy.rst
+.. [acpi-dsd-properties-rules]
+   Documentation/firmware-guide/acpi/DSD-properties-rules.rst
+.. [motorcomm-yt8xxx]
+   Documentation/devicetree/bindings/net/motorcomm,yt8xxx.yaml
diff --git a/Documentation/firmware-guide/acpi/dsd/phy.rst b/Documentation/firmware-guide/acpi/dsd/phy.rst
new file mode 100644
index 000000000..673ac374f
--- /dev/null
+++ b/Documentation/firmware-guide/acpi/dsd/phy.rst
@@ -0,0 +1,201 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================
+MDIO bus and PHYs in ACPI
+=========================
+
+The PHYs on an MDIO bus [phy] are probed and registered using
+fwnode_mdiobus_register_phy().
+
+Later, for connecting these PHYs to their respective MACs, the PHYs registered
+on the MDIO bus have to be referenced.
+
+This document introduces two _DSD properties that are to be used
+for connecting PHYs on the MDIO bus [dsd-properties-rules] to the MAC layer.
+
+These properties are defined in accordance with the "Device
+Properties UUID For _DSD" [dsd-guide] document and the
+daffd814-6eba-4d8c-8a91-bc9bbf4aa301 UUID must be used in the Device
+Data Descriptors containing them.
+
+phy-handle
+----------
+For each MAC node, a device property "phy-handle" is used to reference
+the PHY that is registered on an MDIO bus. This is mandatory for
+network interfaces that have PHYs connected to MAC via MDIO bus.
+
+During the MDIO bus driver initialization, PHYs on this bus are probed
+using the _ADR object as shown below and are registered on the MDIO bus.
+
+.. code-block:: none
+
+      Scope(\_SB.MDI0)
+      {
+        Device(PHY1) {
+          Name (_ADR, 0x1)
+        } // end of PHY1
+
+        Device(PHY2) {
+          Name (_ADR, 0x2)
+        } // end of PHY2
+      }
+
+Later, during the MAC driver initialization, the registered PHY devices
+have to be retrieved from the MDIO bus. For this, the MAC driver needs
+references to the previously registered PHYs which are provided
+as device object references (e.g. \_SB.MDI0.PHY1).
+
+phy-mode
+--------
+The "phy-mode" _DSD property is used to describe the connection to
+the PHY. The valid values for "phy-mode" are defined in [ethernet-controller].
+
+managed
+-------
+Optional property, which specifies the PHY management type.
+The valid values for "managed" are defined in [ethernet-controller].
+
+fixed-link
+----------
+The "fixed-link" is described by a data-only subnode of the
+MAC port, which is linked in the _DSD package via
+hierarchical data extension (UUID dbb8e3e6-5886-4ba6-8795-1319f52a966b
+in accordance with [dsd-guide] "_DSD Implementation Guide" document).
+The subnode should comprise a required property ("speed") and
+possibly the optional ones - complete list of parameters and
+their values are specified in [ethernet-controller].
+
+The following ASL example illustrates the usage of these properties.
+
+DSDT entry for MDIO node
+------------------------
+
+The MDIO bus has an SoC component (MDIO controller) and a platform
+component (PHYs on the MDIO bus).
+
+a) Silicon Component
+This node describes the MDIO controller, MDI0
+---------------------------------------------
+
+.. code-block:: none
+
+	Scope(_SB)
+	{
+	  Device(MDI0) {
+	    Name(_HID, "NXP0006")
+	    Name(_CCA, 1)
+	    Name(_UID, 0)
+	    Name(_CRS, ResourceTemplate() {
+	      Memory32Fixed(ReadWrite, MDI0_BASE, MDI_LEN)
+	      Interrupt(ResourceConsumer, Level, ActiveHigh, Shared)
+	       {
+		 MDI0_IT
+	       }
+	    }) // end of _CRS for MDI0
+	  } // end of MDI0
+	}
+
+b) Platform Component
+The PHY1 and PHY2 nodes represent the PHYs connected to MDIO bus MDI0
+---------------------------------------------------------------------
+
+.. code-block:: none
+
+	Scope(\_SB.MDI0)
+	{
+	  Device(PHY1) {
+	    Name (_ADR, 0x1)
+	  } // end of PHY1
+
+	  Device(PHY2) {
+	    Name (_ADR, 0x2)
+	  } // end of PHY2
+	}
+
+DSDT entries representing MAC nodes
+-----------------------------------
+
+Below are the MAC nodes where PHY nodes are referenced.
+phy-mode and phy-handle are used as explained earlier.
+------------------------------------------------------
+
+.. code-block:: none
+
+	Scope(\_SB.MCE0.PR17)
+	{
+	  Name (_DSD, Package () {
+	     ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		 Package () {
+		     Package (2) {"phy-mode", "rgmii-id"},
+		     Package (2) {"phy-handle", \_SB.MDI0.PHY1}
+	      }
+	   })
+	}
+
+	Scope(\_SB.MCE0.PR18)
+	{
+	  Name (_DSD, Package () {
+	    ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		Package () {
+		    Package (2) {"phy-mode", "rgmii-id"},
+		    Package (2) {"phy-handle", \_SB.MDI0.PHY2}}
+	    }
+	  })
+	}
+
+MAC node example where "managed" property is specified.
+-------------------------------------------------------
+
+.. code-block:: none
+
+	Scope(\_SB.PP21.ETH0)
+	{
+	  Name (_DSD, Package () {
+	     ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		 Package () {
+		     Package () {"phy-mode", "sgmii"},
+		     Package () {"managed", "in-band-status"}
+		 }
+	   })
+	}
+
+MAC node example with a "fixed-link" subnode.
+---------------------------------------------
+
+.. code-block:: none
+
+	Scope(\_SB.PP21.ETH1)
+	{
+	  Name (_DSD, Package () {
+	    ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		 Package () {
+		     Package () {"phy-mode", "sgmii"},
+		 },
+	    ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+		 Package () {
+		     Package () {"fixed-link", "LNK0"}
+		 }
+	  })
+	  Name (LNK0, Package(){ // Data-only subnode of port
+	    ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+		 Package () {
+		     Package () {"speed", 1000},
+		     Package () {"full-duplex", 1}
+		 }
+	  })
+	}
+
+References
+==========
+
+[phy] Documentation/networking/phy.rst
+
+[dsd-properties-rules]
+    Documentation/firmware-guide/acpi/DSD-properties-rules.rst
+
+[ethernet-controller]
+    Documentation/devicetree/bindings/net/ethernet-controller.yaml
+
+[dsd-guide] DSD Guide.
+    https://github.com/UEFI/DSD-Guide/blob/main/dsd-guide.adoc, referenced
+    2021-11-30.