dt-bindings: Add support for Broadcom USB pin map driver

Add DT bindings for the Broadcom USB pin map driver. This driver allows
some USB input and output signals to be mapped to any GPIO instead
of the normal dedicated pins to/from the XHCI controller.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Al Cooper <alcooperx@gmail.com>
Link: https://lore.kernel.org/r/20201012200007.8862-2-alcooperx@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/brcm,usb-pinmap.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/usb/brcm,usb-pinmap.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom USB pin map Controller Device Tree Bindings
+
+maintainers:
+  - Al Cooper <alcooperx@gmail.com>
+
+properties:
+  compatible:
+    items:
+      - const: brcm,usb-pinmap
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+    description: Interrupt for signals mirrored to out-gpios.
+
+  in-gpios:
+    description: Array of one or two GPIO pins used for input signals.
+
+  brcm,in-functions:
+    $ref: /schemas/types.yaml#/definitions/string-array
+    description: Array of input signal names, one per gpio in in-gpios.
+
+  brcm,in-masks:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    description: Array of enable and mask pairs, one per gpio in-gpios.
+
+  out-gpios:
+    description: Array of one GPIO pin used for output signals.
+
+  brcm,out-functions:
+    $ref: /schemas/types.yaml#/definitions/string-array
+    description: Array of output signal names, one per gpio in out-gpios.
+
+  brcm,out-masks:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    description: Array of enable, value, changed and clear masks, one
+      per gpio in out-gpios.
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+dependencies:
+  in-gpios: [ interrupts ]
+
+examples:
+  - |
+    usb_pinmap: usb-pinmap@22000d0 {
+        compatible = "brcm,usb-pinmap";
+        reg = <0x22000d0 0x4>;
+        in-gpios = <&gpio 18 0>, <&gpio 19 0>;
+        brcm,in-functions = "VBUS", "PWRFLT";
+        brcm,in-masks = <0x8000 0x40000 0x10000 0x80000>;
+        out-gpios = <&gpio 20 0>;
+        brcm,out-functions = "PWRON";
+        brcm,out-masks = <0x20000 0x800000 0x400000 0x200000>;
+        interrupts = <0x0 0xb2 0x4>;
+    };
+
+...