dt-bindings: usb: Add binding for Cypress HX3 USB 3.0 family

The HX3 family comes in different variants (up to 4 USB 3.0 ports;
multi-TT), e.g. CYUSB330x/CYUSB331x/CYUSB332x/CYUSB230x.

This initial version of the binding only describes USB related aspects
of the HX3 family, it does not cover the option of connecting the
controller as an i2c slave.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Benjamin Bara <benjamin.bara@skidata.com>
Link: https://lore.kernel.org/r/20230620-hx3-v7-3-f79b4b22a1bf@skidata.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/cypress,hx3.yaml

+# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/usb/cypress,hx3.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Cypress HX3 USB 3.0 hub controller family
+
+maintainers:
+  - Benjamin Bara <benjamin.bara@skidata.com>
+
+allOf:
+  - $ref: usb-device.yaml#
+
+properties:
+  compatible:
+    enum:
+      - usb4b4,6504
+      - usb4b4,6506
+
+  reg: true
+
+  reset-gpios:
+    items:
+      - description: GPIO specifier for RESETN pin.
+
+  vdd-supply:
+    description:
+      1V2 power supply (VDD_EFUSE, AVDD12, DVDD12).
+
+  vdd2-supply:
+    description:
+      3V3 power supply (AVDD33, VDD_IO).
+
+  peer-hub:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      phandle to the peer hub on the controller.
+
+required:
+  - compatible
+  - reg
+  - peer-hub
+  - vdd-supply
+  - vdd2-supply
+
+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 = "usb4b4,6504";
+          reg = <1>;
+          peer-hub = <&hub_3_0>;
+          reset-gpios = <&gpio1 11 GPIO_ACTIVE_LOW>;
+          vdd-supply = <&reg_1v2_usb>;
+          vdd2-supply = <&reg_3v3_usb>;
+        };
+
+        /* 3.0 hub on port 2 */
+        hub_3_0: hub@2 {
+          compatible = "usb4b4,6506";
+          reg = <2>;
+          peer-hub = <&hub_2_0>;
+          reset-gpios = <&gpio1 11 GPIO_ACTIVE_LOW>;
+          vdd-supply = <&reg_1v2_usb>;
+          vdd2-supply = <&reg_3v3_usb>;
+        };
+    };