dt-bindings: Document Marvell Aquantia PHY

Document bindings for Marvell Aquantia PHY.

The Marvell Aquantia PHY require a firmware to work correctly and there
at least 3 way to load this firmware.

Describe all the different way and document the binding "firmware-name"
to load the PHY firmware from userspace.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/marvell,aquantia.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/marvell,aquantia.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Marvell Aquantia Ethernet PHY
+
+maintainers:
+  - Christian Marangi <ansuelsmth@gmail.com>
+
+description: |
+  Marvell Aquantia Ethernet PHY require a firmware to be loaded to actually
+  work.
+
+  This can be done and is implemented by OEM in 3 different way:
+    - Attached SPI flash directly to the PHY with the firmware. The PHY
+      will self load the firmware in the presence of this configuration.
+    - Read from a dedicated partition on system NAND declared in an
+      NVMEM cell, and loaded to the PHY using its mailbox interface.
+    - Manually provided firmware loaded from a file in the filesystem.
+
+allOf:
+  - $ref: ethernet-phy.yaml#
+
+select:
+  properties:
+    compatible:
+      contains:
+        enum:
+          - ethernet-phy-id03a1.b445
+          - ethernet-phy-id03a1.b460
+          - ethernet-phy-id03a1.b4a2
+          - ethernet-phy-id03a1.b4d0
+          - ethernet-phy-id03a1.b4e0
+          - ethernet-phy-id03a1.b5c2
+          - ethernet-phy-id03a1.b4b0
+          - ethernet-phy-id03a1.b662
+          - ethernet-phy-id03a1.b712
+          - ethernet-phy-id31c3.1c12
+  required:
+    - compatible
+
+properties:
+  reg:
+    maxItems: 1
+
+  firmware-name:
+    description: specify the name of PHY firmware to load
+
+  nvmem-cells:
+    description: phandle to the firmware nvmem cell
+    maxItems: 1
+
+  nvmem-cell-names:
+    const: firmware
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    mdio {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ethernet-phy@0 {
+            compatible = "ethernet-phy-id31c3.1c12",
+                         "ethernet-phy-ieee802.3-c45";
+
+            reg = <0>;
+            firmware-name = "AQR-G4_v5.4.C-AQR_CIG_WF-1945_0x8_ID44776_VER1630.cld";
+        };
+
+        ethernet-phy@1 {
+            compatible = "ethernet-phy-id31c3.1c12",
+                         "ethernet-phy-ieee802.3-c45";
+
+            reg = <1>;
+            nvmem-cells = <&aqr_fw>;
+            nvmem-cell-names = "firmware";
+        };
+    };
+
+    flash {
+        compatible = "jedec,spi-nor";
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        partitions {
+            compatible = "fixed-partitions";
+            #address-cells = <1>;
+            #size-cells = <1>;
+
+            /* ... */
+
+            partition@650000 {
+                compatible = "nvmem-cells";
+                label = "0:ethphyfw";
+                reg = <0x650000 0x80000>;
+                read-only;
+                #address-cells = <1>;
+                #size-cells = <1>;
+
+                aqr_fw: aqr_fw@0 {
+                    reg = <0x0 0x5f42a>;
+                };
+            };
+
+            /* ... */
+
+        };
+    };