dt-bindings: reset: Document RZ/G2L USBPHY Control bindings

Add device tree binding document for RZ/G2L USBPHY Control Device.
It mainly controls reset and power down of the USB/PHY.
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210719121938.6532-4-biju.das.jz@bp.renesas.comSigned-off-by: Philipp Zabel <p.zabel@pengutronix.de>

Documentation/devicetree/bindings/reset/renesas,rzg2l-usbphy-ctrl.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/reset/renesas,rzg2l-usbphy-ctrl.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Renesas RZ/G2L USBPHY Control
+
+maintainers:
+  - Biju Das <biju.das.jz@bp.renesas.com>
+
+description:
+  The RZ/G2L USBPHY Control mainly controls reset and power down of the
+  USB/PHY.
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - renesas,r9a07g044-usbphy-ctrl # RZ/G2{L,LC}
+      - const: renesas,rzg2l-usbphy-ctrl
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  resets:
+    maxItems: 1
+
+  power-domains:
+    maxItems: 1
+
+  '#reset-cells':
+    const: 1
+    description: |
+      The phandle's argument in the reset specifier is the PHY reset associated
+      with the USB port.
+      0 = Port 1 Phy reset
+      1 = Port 2 Phy reset
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - resets
+  - power-domains
+  - '#reset-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/r9a07g044-cpg.h>
+
+    phyrst: usbphy-ctrl@11c40000 {
+        compatible = "renesas,r9a07g044-usbphy-ctrl",
+                     "renesas,rzg2l-usbphy-ctrl";
+        reg = <0x11c40000 0x10000>;
+        clocks = <&cpg CPG_MOD R9A07G044_USB_PCLK>;
+        resets = <&cpg R9A07G044_USB_PRESETN>;
+        power-domains = <&cpg>;
+        #reset-cells = <1>;
+    };