dt-bindings: usb: Introduce usb-hub.yaml

Introduce a general USB hub binding that describes downstream ports
and hard wired USB devices for on-board USB hubs.

Signed-off-by: Pin-yen Lin <[e-mail]>
Reviewed-by: "Rob Herring (Arm)" <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/usb/usb-hub.yaml

···
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/usb/usb-hub.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic USB Hub
+
+maintainers:
+  - Pin-yen Lin <[e-mail]>
+
+allOf:
+  - $ref: usb-device.yaml#
+
+properties:
+  '#address-cells':
+    const: 1
+
+  peer-hub:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      phandle to the peer hub on the controller.
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+    description:
+      The downstream facing USB ports
+
+    patternProperties:
+      "^port@[1-9a-f][0-9a-f]*$":
+        $ref: /schemas/graph.yaml#/properties/port
+
+patternProperties:
+  '^.*@[1-9a-f][0-9a-f]*$':
+    description: The hard wired USB devices
+    type: object
+    $ref: /schemas/usb/usb-device.yaml
+    additionalProperties: true
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: true
+
+examples:
+  - |
+    usb {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        /* 2.0 hub on port 1 */
+        hub_2_0: hub@1 {
+            compatible = "usb123,4567";
+            reg = <1>;
+            peer-hub = <&hub_3_0>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+            /* USB 2.0 device on port 5 */
+            device@5 {
+                reg = <5>;
+                compatible = "usb765,4321";
+            };
+        };
+
+        /* 3.0 hub on port 2 */
+        hub_3_0: hub@2 {
+            compatible = "usb123,abcd";
+            reg = <2>;
+            peer-hub = <&hub_2_0>;
+
+            ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                /* Type-A connector on port 3 */
+                port@3 {
+                    reg = <3>;
+                    endpoint {
+                        remote-endpoint = <&usb_a0_ss>;
+                    };
+                };
+            };
+        };
+    };