docs: acpi: dsd: add Motorcomm yt8xxx PHY properties

Document Motorcomm yt8xxx PHY ACPI _DSD properties consumed by
the motorcomm PHY driver.

Describe property placement, UUID usage, and reference the DT binding
for value constraints and defaults.

Signed-off-by: chunzhi.lin <linchunzhi0@gmail.com>

Changes in v2:
- Keep dsd/ entries sorted in Documentation/firmware-guide/acpi/index.rst

Link: https://patch.msgid.link/20260507040221.3679454-3-linchunzhi0@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

Documentation/firmware-guide/acpi/index.rst

@@ -11,6 +11,7 @@ ACPI Support
    dsd/graph
    dsd/data-node-references
    dsd/leds
+   dsd/motorcomm-yt8xxx-phy
    dsd/phy
    enumeration
    osi