regulator: Add dt-binding for QCOM PMIC VBUS output regulator

This describes how to enable the Qualcomm PMIC VBUS booster used for
providing power to connected USB peripherals when the USB role is host
mode.  The driver itself will register the vbus_usb regulator, so that
external drivers can utilize the enable/disable regulator APIs.
Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
Link: https://lore.kernel.org/r/20200626185516.18018-6-wcheng@codeaurora.orgSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/qcom,usb-vbus-regulator.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/qcom,usb-vbus-regulator.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: The Qualcomm PMIC VBUS output regulator driver
+
+maintainers:
+  - Wesley Cheng <wcheng@codeaurora.org>
+
+description: |
+  This regulator driver controls the VBUS output by the Qualcomm PMIC.  This
+  regulator will be enabled in situations where the device is required to
+  provide power to the connected peripheral.
+
+properties:
+  compatible:
+    enum:
+      - qcom,pm8150b-vbus-reg
+
+  reg:
+    maxItems: 1
+    description: VBUS output base address
+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+     pm8150b {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        pm8150b_vbus: dcdc@1100 {
+            compatible = "qcom,pm8150b-vbus-reg";
+            reg = <0x1100>;
+        };
+     };
+...