diff --git a/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml b/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
index fbe2ddcdd909..17fe2edf4886 100644
--- a/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
+++ b/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
@@ -130,6 +130,42 @@ patternProperties:
         maximum: 4
         description: GMAC port identifier
 
+    allOf:
+      - if:
+          properties:
+            reg:
+              contains:
+                items:
+                  - enum:
+                      - 3
+                      - 4
+        then:
+          properties:
+            '#address-cells':
+              const: 1
+
+            '#size-cells':
+              const: 0
+
+          patternProperties:
+            "^ethernet@[0-5]$":
+              type: object
+              unevaluatedProperties: false
+              $ref: ethernet-controller.yaml#
+              description: External ethernet port ID available on the GDM port
+
+              properties:
+                compatible:
+                  const: airoha,eth-port
+
+                reg:
+                  maximum: 5
+                  description: External ethernet port identifier
+
+              required:
+                - reg
+                - compatible
+
     required:
       - reg
       - compatible
@@ -191,9 +227,27 @@ examples:
         #address-cells = <1>;
         #size-cells = <0>;
 
-        mac: ethernet@1 {
+        ethernet@1 {
           compatible = "airoha,eth-mac";
           reg = <1>;
         };
+
+        ethernet@4 {
+          compatible = "airoha,eth-mac";
+          reg = <4>;
+
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          ethernet@0 {
+            compatible = "airoha,eth-port";
+            reg = <0>;
+          };
+
+          ethernet@1 {
+            compatible = "airoha,eth-port";
+            reg = <1>;
+          };
+        };
       };
     };