Document support for Airoha AN8855 PBUS MDIO. Airoha AN8855 Switch
expose a way to access internal PHYs via Switch register.
This is named internally PBUS and does the function of an MDIO bus
for the internal PHYs.

It does support a maximum of 5 PHYs (matching the number of port
the Switch support)

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 .../bindings/net/airoha,an8855-mdio.yaml      | 57 +++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/net/airoha,an8855-mdio.yaml

diff --git a/Documentation/devicetree/bindings/net/airoha,an8855-mdio.yaml b/Documentation/devicetree/bindings/net/airoha,an8855-mdio.yaml
new file mode 100644
index 000000000000..c873103d2b66
--- /dev/null
+++ b/Documentation/devicetree/bindings/net/airoha,an8855-mdio.yaml
@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/airoha,an8855-mdio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Airoha AN8855 PBUS MDIO
+
+maintainers:
+  - Christian Marangi <ansuelsmth@gmail.com>
+
+description:
+  Airoha AN8855 Switch expose a way to access internal PHYs via
+  Switch register. This is named internally PBUS and does the function
+  of an MDIO bus for the internal PHYs.
+
+  It does support a maximum of 5 PHYs (matching the number of port
+  the Switch support)
+
+$ref: /schemas/net/mdio.yaml#
+
+properties:
+  compatible:
+    const: airoha,an8855-mdio
+
+required:
+  - compatible
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    mdio {
+        compatible = "airoha,an8855-mdio";
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        internal_phy1: phy@1 {
+            reg = <1>;
+        };
+
+        internal_phy2: phy@2 {
+            reg = <2>;
+        };
+
+        internal_phy3: phy@3 {
+            reg = <3>;
+        };
+
+        internal_phy4: phy@4 {
+            reg = <4>;
+        };
+
+        internal_phy5: phy@5 {
+            reg = <5>;
+        };
+    };
-- 
2.48.1