EN7581 and AN7583 SoCs support connecting multiple external SerDes to GDM3
or GDM4 ports via a hw arbiter 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 arbiter 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 arbiter and are represented
by ethernet property.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 .../devicetree/bindings/net/airoha,en7581-eth.yaml | 52 +++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml b/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
index fbe2ddcdd909..73ba37872247 100644
--- a/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
+++ b/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
@@ -130,6 +130,38 @@ patternProperties:
         maximum: 4
         description: GMAC port identifier
 
+      '#address-cells':
+        const: 1
+      '#size-cells':
+        const: 0
+
+    allOf:
+      - if:
+          properties:
+            reg:
+              items:
+                - enum:
+                    - 3
+                    - 4
+        then:
+          patternProperties:
+            "^ethernet-port@[0-5]$":
+              type: object
+              unevaluatedProperties: false
+              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 +223,27 @@ 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>;
+          };
+        };
       };
     };

-- 
2.54.0