regulator: dt-bindings: Add Richtek RT4803

Add the binding document for Richtek RT4803.
Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/1680050606-461-1-git-send-email-cy_huang@richtek.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/richtek,rt4803.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/richtek,rt4803.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Richtek RT4803 Boost Regulator
+
+maintainers:
+  - ChiYuan Huang <cy_huang@richtek.com>
+
+description: |
+  RT4803 is a boost regulator that's designed to provide the minimum output
+  voltage, even if the input voltage is lower than the required voltage. It
+  supports boost and auto bypass mode that depends on the difference between the
+  input and output voltage. If the input is lower than the output, mode will
+  transform to boost mode. Otherwise, turn on bypass switch to enter bypass mode.
+
+  Datasheet is available at
+  https://www.richtek.com/assets/product_file/RT4803/DS4803-03.pdf
+  https://www.richtek.com/assets/product_file/RT4803A/DS4803A-06.pdf
+
+allOf:
+  - $ref: regulator.yaml#
+
+properties:
+  compatible:
+    enum:
+      - richtek,rt4803
+
+  reg:
+    maxItems: 1
+
+  richtek,vsel-active-high:
+    type: boolean
+    description: Specify the VSEL register group is using when system is active
+
+  regulator-allowed-modes:
+    description: |
+      Available operating mode
+        1: Auto PFM/PWM
+        2: Force PWM
+    items:
+      enum: [1, 2]
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      regulator@75 {
+        compatible = "richtek,rt4803";
+        reg = <0x75>;
+        richtek,vsel-active-high;
+        regulator-name = "rt4803-regulator";
+        regulator-min-microvolt = <2850000>;
+        regulator-max-microvolt = <4400000>;
+        regulator-allowed-modes = <1 2>;
+        regulator-always-on;
+      };
+    };