dt-bindings: usb: add bindings for microchip mpfs musb

Add device tree bindings for the usb controller on
the Microchip PolarFire SoC.

Signed-off-by: Conor Dooley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/usb/microchip,mpfs-musb.yaml

···
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/usb/microchip,mpfs-musb.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip MPFS USB Controller Device Tree Bindings
+
+allOf:
+  - $ref: usb-drd.yaml#
+
+maintainers:
+  - Conor Dooley <[e-mail]>
+
+properties:
+  compatible:
+    enum:
+      - microchip,mpfs-musb
+
+  dr_mode: true
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    minItems: 2
+    maxItems: 2
+
+  interrupt-names:
+    items:
+      - const: dma
+      - const: mc
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-names
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    #include "dt-bindings/clock/microchip,mpfs-clock.h"
+    usb@20201000 {
+        compatible = "microchip,mpfs-musb";
+        reg = <0x20201000 0x1000>;
+        clocks = <&clkcfg CLK_USB>;
+        interrupt-parent = <&plic>;
+        interrupts = <86>, <87>;
+        interrupt-names = "dma", "mc";
+        dr_mode = "host";
+    };
+
+...