regulator: rtq2134: Add binding document for Richtek RTQ2134 SubPMIC

Add binding document for Richtek RTQ2134 SubPMIC.
Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
Link: https://lore.kernel.org/r/1626422636-29458-1-git-send-email-u0084500@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/richtek,rtq2134-regulator.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/richtek,rtq2134-regulator.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Richtek RTQ2134 SubPMIC Regulator
+
+maintainers:
+  - ChiYuan Huang <cy_huang@richtek.com>
+
+description: |
+  The RTQ2134 is a multi-phase, programmable power management IC that
+  integrates with four high efficient, synchronous step-down converter cores.
+
+  Datasheet is available at
+  https://www.richtek.com/assets/product_file/RTQ2134-QA/DSQ2134-QA-01.pdf
+
+properties:
+  compatible:
+    enum:
+      - richtek,rtq2134
+
+  reg:
+    maxItems: 1
+
+  regulators:
+    type: object
+
+    patternProperties:
+      "^buck[1-3]$":
+        type: object
+        $ref: regulator.yaml#
+        description: |
+          regulator description for buck[1-3].
+
+        properties:
+          richtek,use-vsel-dvs:
+            type: boolean
+            description: |
+              If specified, buck will listen to 'vsel' pin for dvs config.
+              Else, use dvs0 voltage by default.
+
+          richtek,uv-shutdown:
+            type: boolean
+            description: |
+              If specified, use shutdown as UV action. Else, hiccup by default.
+
+        unevaluatedProperties: false
+
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - regulators
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      rtq2134@18 {
+        compatible = "richtek,rtq2134";
+        reg = <0x18>;
+
+        regulators {
+          buck1 {
+            regulator-name = "rtq2134-buck1";
+            regulator-min-microvolt = <300000>;
+            regulator-max-microvolt = <1850000>;
+            regulator-always-on;
+            richtek,use-vsel-dvs;
+            regulator-state-mem {
+              regulator-suspend-min-microvolt = <550000>;
+              regulator-suspend-max-microvolt = <550000>;
+            };
+          };
+          buck2 {
+            regulator-name = "rtq2134-buck2";
+            regulator-min-microvolt = <1120000>;
+            regulator-max-microvolt = <1120000>;
+            regulator-always-on;
+            richtek,use-vsel-dvs;
+            regulator-state-mem {
+              regulator-suspend-min-microvolt = <1120000>;
+              regulator-suspend-max-microvolt = <1120000>;
+            };
+          };
+          buck3 {
+            regulator-name = "rtq2134-buck3";
+            regulator-min-microvolt = <600000>;
+            regulator-max-microvolt = <600000>;
+            regulator-always-on;
+            richtek,use-vsel-dvs;
+            regulator-state-mem {
+              regulator-suspend-min-microvolt = <600000>;
+              regulator-suspend-max-microvolt = <600000>;
+            };
+          };
+        };
+      };
+    };