regulator: rt6160: Add DT binding document for Richtek RT6160

Add DT binding document for Richtek RT6160 voltage regulator.
Signed-off-by: NChiYuan Huang <cy_huang@richtek.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1622611906-2403-1-git-send-email-u0084500@gmail.comSigned-off-by: NMark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/richtek,rt6160-regulator.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/richtek,rt6160-regulator.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Richtek RT6160 BuckBoost converter
+
+maintainers:
+  - ChiYuan Huang <cy_huang@richtek.com>
+
+description: |
+  The RT6160 is a high-efficiency buck-boost converter that can provide
+  up to 3A output current from 2025mV to 5200mV. And it support the wide
+  input voltage range from 2200mV to 5500mV.
+
+  Datasheet is available at
+  https://www.richtek.com/assets/product_file/RT6160A/DS6160A-00.pdf
+
+allOf:
+  - $ref: regulator.yaml#
+
+properties:
+  compatible:
+    enum:
+      - richtek,rt6160
+
+  reg:
+    maxItems: 1
+
+  enable-gpios:
+    description: A connection of the 'enable' gpio line.
+    maxItems: 1
+
+  richtek,vsel-active-low:
+    description: |
+      Used to indicate the 'vsel' pin active level. if not specified, use
+      high active level as the default.
+    type: boolean
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      rt6160@75 {
+        compatible = "richtek,rt6160";
+        reg = <0x75>;
+        enable-gpios = <&gpio26 2 0>;
+        regulator-name = "rt6160-buckboost";
+        regulator-min-microvolt = <2025000>;
+        regulator-max-microvolt = <5200000>;
+      };
+    };