regulator: Add bindings for Richtek RT6190 regulator

Add devicetree binding for Richtek RT6190 4-Switch buckboost controller.
Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1667183334-16511-2-git-send-email-u0084500@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/richtek,rt6190.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/richtek,rt6190.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Richtek RT6190 4-Switch BuckBoost controller
+
+maintainers:
+  - ChiYuan Huang <cy_huang@richtek.com>
+
+description: |
+  The RT6190 is 4-Switch BuckBoost controller designed for converting input
+  voltage to output voltage that can be equal to, higher or lower than input
+  voltage. It operates with wide input voltage range from 4.5V to 36V, and
+  the output voltage can be set from 3V to 36V by external FB pin. It's commonly
+  used for the application like as BuckBoost bus supply, docking station and USB
+  power delivery product.
+
+  Datasheet is available at
+  https://www.richtek.com/assets/product_file/RT6190/DS6190-02.pdf
+
+allOf:
+  - $ref: regulator.yaml#
+
+properties:
+  compatible:
+    enum:
+      - richtek,rt6190
+
+  reg:
+    maxItems: 1
+
+  enable-gpios:
+    maxItems: 1
+
+  wakeup-source: true
+
+  interrupts:
+    maxItems: 1
+
+  regulator-allowed-modes:
+    description: |
+      buck allowed operating mode
+        0: PSM mode (light load Power Saving Mode)
+        1: FCCM mode (Forced-CCM mode)
+    maxItems: 2
+    items:
+      enum: [0, 1]
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      regulator@2c {
+        compatible = "richtek,rt6190";
+        reg = <0x2c>;
+        wakeup-source;
+        interrupts-extended = <&gpio26 0 IRQ_TYPE_LEVEL_LOW>;
+        enable-gpios = <&gpio26 1 GPIO_ACTIVE_HIGH>;
+        regulator-name = "richtek,rt6190-buckboost";
+        regulator-min-microvolt = <3000000>;
+        regulator-max-microvolt = <32000000>;
+        regulator-min-microamp = <306000>;
+        regulator-max-microamp = <12114000>;
+        regulator-allowed-modes = <0 1>;
+      };
+    };