dt-bindings: usb: Add downstream facing ports to realtek binding

Add a graph with 4 output endpoints to this hub binding to support the
scenario where a downstream facing port is connected to a device that
isn't a connector or a USB device with a VID:PID. This will be used to
connect downstream facing ports to USB type-c switches so the USB
superspeed and high speed lanes can be put onto USB connectors.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: linux-usb@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: Pin-yen Lin <treapking@chromium.org>
Cc: maciek swiech <drmasquatch@google.com>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20240223005823.3074029-2-swboyd@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/realtek,rts5411.yaml

@@ -21,6 +21,12 @@ properties:
 
   reg: true
 
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
   vdd-supply:
     description:
       phandle to the regulator that provides power to the hub.
@@ -30,6 +36,36 @@ properties:
     description:
       phandle to the peer hub on the controller.
 
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description:
+          1st downstream facing USB port
+
+      port@2:
+        $ref: /schemas/graph.yaml#/properties/port
+        description:
+          2nd downstream facing USB port
+
+      port@3:
+        $ref: /schemas/graph.yaml#/properties/port
+        description:
+          3rd downstream facing USB port
+
+      port@4:
+        $ref: /schemas/graph.yaml#/properties/port
+        description:
+          4th downstream facing USB port
+
+patternProperties:
+  '^.*@[1-4]$':
+    description: The hard wired USB devices
+    type: object
+    $ref: /schemas/usb/usb-device.yaml
+
 required:
   - peer-hub
   - compatible
@@ -50,6 +86,13 @@ examples:
             reg = <1>;
             vdd-supply = <&pp3300_hub>;
             peer-hub = <&hub_3_0>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+            /* USB 2.0 device on port 2 */
+            device@2 {
+                compatible = "usb123,4567";
+                reg = <2>;
+            };
         };
 
         /* 3.0 hub on port 2 */
@@ -58,5 +101,17 @@ examples:
             reg = <2>;
             vdd-supply = <&pp3300_hub>;
             peer-hub = <&hub_2_0>;
+
+            ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                /* Type-A connector on port 4 */
+                port@4 {
+                    reg = <4>;
+                    endpoint {
+                      remote-endpoint = <&usb_a0_ss>;
+                    };
+                };
+            };
         };
     };