The Realtek Otto switch family provides different numbers of MDIO
buses. RTL838x has one bus, RTL839x has two buses, and RTL930x/RTL931x
have four buses.

The binding currently accepts mdio-bus@0 through mdio-bus@3 for every
supported compatible, allowing non-existent buses to be described for
RTL838x and RTL839x devices.

Select the permitted bus node names based on the controller compatible.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
---
 .../bindings/net/realtek,rtl9301-mdio.yaml    | 24 +++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml b/Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml
index 67e0b23a8470..7f5b4897487b 100644
--- a/Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml
+++ b/Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml
@@ -67,6 +67,30 @@ patternProperties:
 
     unevaluatedProperties: false
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - realtek,rtl8380-mdio
+              - realtek,rtl8381-mdio
+              - realtek,rtl8382-mdio
+    then:
+      patternProperties:
+        '^mdio-bus@[1-3]$': false
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - realtek,rtl8391-mdio
+              - realtek,rtl8392-mdio
+              - realtek,rtl8393-mdio
+    then:
+      patternProperties:
+        '^mdio-bus@[2-3]$': false
+
 required:
   - compatible
   - reg
-- 
2.55.0