EN7581 and AN7583 SoCs support connecting multiple external SerDes to GDM3
or GDM4 ports via a hw multiplexer that manages the traffic in a TDM
manner. As a result multiple net_devices can connect to the same GDM{3,4}
port and there is a theoretical "1:n" relation between GDM ports and
net_devices.
Introduce the ethernet-port property in order to model a given net_device
that is connected via the external multiplexer to the GDM{3,4} port (that
is represented by the ethernet property. Please note GDM1 or GDM2 does not
support the connection with the external multiplexer and are represented
by ethernet property.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 .../devicetree/bindings/net/airoha,en7581-eth.yaml | 44 +++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml b/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
index fbe2ddcdd909cb3d853a4ab9e9fec4af1d096c52..ebbd433e9c9fbfaefd8d07c3678cabc91574d125 100644
--- a/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
+++ b/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
@@ -130,6 +130,30 @@ patternProperties:
         maximum: 4
         description: GMAC port identifier
 
+      '#address-cells':
+        const: 1
+      '#size-cells':
+        const: 0
+
+    patternProperties:
+      "^ethernet-port@[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:
+            maxItems: 1
+            description: External ethernet port identifier
+
+        required:
+          - compatible
+          - reg
+
     required:
       - reg
       - compatible
@@ -191,9 +215,27 @@ examples:
         #address-cells = <1>;
         #size-cells = <0>;
 
-        mac: ethernet@1 {
+        mac1: ethernet@1 {
           compatible = "airoha,eth-mac";
           reg = <1>;
         };
+
+        mac4: ethernet@4 {
+          compatible = "airoha,eth-mac";
+          reg = <4>;
+
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          ethernet-port@0 {
+            compatible = "airoha,eth-port";
+            reg = <0>;
+          };
+
+          ethernet-port@1 {
+            compatible = "airoha,eth-port";
+            reg = <1>;
+          };
+        };
       };
     };

-- 
2.53.0