dt-bindings: usb: Add binding for Via lab VL817 hub controller

The VIA Lab VL817 is a USB 3.1 Gen 1 hub and USB 2.0 hub
controller that features 4 downstream ports and 1 otg, with
an internal 5V regulator and has external reset pin.

Add a device tree binding for its USB protocol part.
The internal LDO is not covered by this and can just be modelled
as a fixed regulator.

Add combo of USB 2.0 and USB 3.0 root hub using peer-hub.
Signed-off-by: Anand Moon <linux.amoon@gmail.com>
Link: https://lore.kernel.org/r/20230118044418.875-7-linux.amoon@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/vialab,vl817.yaml

+# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/usb/vialab,vl817.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Via labs VL817 USB 3.1 hub controller
+
+maintainers:
+  - Anand Moon <linux.amoon@gmail.com>
+
+allOf:
+  - $ref: usb-device.yaml#
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - usb2109,2817
+          - usb2109,817
+
+  reg: true
+
+  reset-gpios:
+    description: GPIO controlling the RESET# pin.
+
+  vdd-supply:
+    description:
+      phandle to the regulator that provides power to the hub.
+
+  peer-hub:
+    $ref: '/schemas/types.yaml#/definitions/phandle'
+    description:
+      phandle to the peer hub on the controller.
+
+required:
+  - peer-hub
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    usb {
+        dr_mode = "host";
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        /* 2.0 hub on port 1 */
+        hub_2_0: hub@1 {
+            compatible = "usb2109,2817";
+            reg = <1>;
+            vdd-supply = <&vcc_5v>;
+            peer-hub = <&hub_3_0>;
+            reset-gpios = <&gpio 20 GPIO_ACTIVE_LOW>;
+        };
+
+        /* 3.1 hub on port 4 */
+        hub_3_0: hub@2 {
+            compatible = "usb2109,817";
+            reg = <2>;
+            vdd-supply = <&vcc_5v>;
+            peer-hub = <&hub_2_0>;
+            reset-gpios = <&gpio 20 GPIO_ACTIVE_LOW>;
+        };
+    };