[PATCH net-next 3/5] dt-bindings: net: Add Realtek MDIO controller

[Chris Packham <chris.packham@alliedtelesis.co.nz>]

Add dtschema for the MDIO controller found in the RTL9300 Ethernet
switch. The controller is slightly unusual in that direct MDIO
communication is not possible. We model the MDIO controller with the
MDIO buses as child nodes and the PHYs as children of the buses. The
mapping of switch port number to MDIO bus/addr requires the
ethernet-ports sibling to provide the mapping via the phy-handle
property.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---

Notes:
    This is technically v7 of [1] and [2] which are combined now that
    rtl9301-switch.yaml under net/ the only change from those is that the
    $ref: in rtl9301-switch.yaml can now use a relative path
    
    I could technically do away with the reg property on the mdio-controller
    node. I don't currently need to use it in my driver and it looks like
    the register offsets are the same between the RTL9300 and RTL9310.
    
    [1] - https://lore.kernel.org/lkml/20250204030249.1965444-6-chris.packham@alliedtelesis.co.nz/
    [2] - https://lore.kernel.org/lkml/20250204030249.1965444-4-chris.packham@alliedtelesis.co.nz/

 .../bindings/net/realtek,rtl9301-mdio.yaml    | 86 +++++++++++++++++++
 .../bindings/net/realtek,rtl9301-switch.yaml  | 31 +++++++
 2 files changed, 117 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml

diff --git a/Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml b/Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml
new file mode 100644
index 000000000000..02e4e33e9969
--- /dev/null
+++ b/Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml
@@ -0,0 +1,86 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/realtek,rtl9301-mdio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Realtek RTL9300 MDIO Controller
+
+maintainers:
+  - Chris Packham <chris.packham@alliedtelesis.co.nz>
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - enum:
+              - realtek,rtl9302b-mdio
+              - realtek,rtl9302c-mdio
+              - realtek,rtl9303-mdio
+          - const: realtek,rtl9301-mdio
+      - const: realtek,rtl9301-mdio
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+  reg:
+    maxItems: 1
+
+patternProperties:
+  '^mdio-bus@[0-3]$':
+    $ref: mdio.yaml#
+
+    properties:
+      reg:
+        maxItems: 1
+
+    required:
+      - reg
+
+    patternProperties:
+      '^ethernet-phy@[a-f0-9]+$':
+        type: object
+        $ref: ethernet-phy.yaml#
+        unevaluatedProperties: false
+
+    unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    mdio-controller@ca00 {
+      compatible = "realtek,rtl9301-mdio";
+      reg = <0xca00 0x200>;
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      mdio-bus@0 {
+        reg = <0>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ethernet-phy@0 {
+          compatible = "ethernet-phy-ieee802.3-c45";
+          reg = <0>;
+        };
+      };
+
+      mdio-bus@1 {
+        reg = <1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ethernet-phy@0 {
+          compatible = "ethernet-phy-ieee802.3-c45";
+          reg = <0>;
+        };
+      };
+    };
diff --git a/Documentation/devicetree/bindings/net/realtek,rtl9301-switch.yaml b/Documentation/devicetree/bindings/net/realtek,rtl9301-switch.yaml
index 5d29647bea2d..80eabc170669 100644
--- a/Documentation/devicetree/bindings/net/realtek,rtl9301-switch.yaml
+++ b/Documentation/devicetree/bindings/net/realtek,rtl9301-switch.yaml
@@ -54,6 +54,9 @@ patternProperties:
   'i2c@[0-9a-f]+$':
     $ref: /schemas/i2c/realtek,rtl9301-i2c.yaml#
 
+  'mdio-controller@[0-9a-f]+$':
+    $ref: realtek,rtl9301-mdio.yaml#
+
 required:
   - compatible
   - reg
@@ -129,15 +132,43 @@ examples:
         };
       };
 
+      mdio-controller@ca00 {
+        compatible = "realtek,rtl9301-mdio";
+        reg = <0xca00 0x200>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        mdio-bus@0 {
+          reg = <0>;
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          phy1: ethernet-phy@0 {
+            reg = <0>;
+          };
+        };
+        mdio-bus@1 {
+          reg = <1>;
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          phy2: ethernet-phy@0 {
+            reg = <0>;
+          };
+        };
+      };
+
       ethernet-ports {
         #address-cells = <1>;
         #size-cells = <0>;
 
         port@0 {
           reg = <0>;
+          phy-handle = <&phy1>;
         };
         port@1 {
           reg = <1>;
+          phy-handle = <&phy2>;
         };
       };
     };
-- 
2.48.1