dt-bindings: net: Add Realtek MDIO controller

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>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250218195216.1034220-4-chris.packham@alliedtelesis.co.nz
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 117 insertions, 0 deletions

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>;
         };
       };
     };