dt-bindings: regulator: Describe Qualcomm REFGEN regulator

Modern Qualcomm SoCs have a REFGEN (reference voltage generator)
regulator, providing reference voltage to on-chip IP, like PHYs.
It's controlled through MMIO and we can toggle it or read its state back.

Describe it.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230628-topic-refgen-v3-1-9fbf0e605d23@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/qcom,sdm845-refgen-regulator.yaml

@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/qcom,sdm845-refgen-regulator.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Qualcomm Technologies, Inc. REFGEN Regulator
+
+maintainers:
+  - Konrad Dybcio <konradybcio@kernel.org>
+
+description:
+  The REFGEN (reference voltage generator) regulator provides reference
+  voltage for on-chip IPs (like PHYs) on some Qualcomm SoCs.
+
+allOf:
+  - $ref: regulator.yaml#
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - enum:
+              - qcom,sc7180-refgen-regulator
+              - qcom,sc8180x-refgen-regulator
+              - qcom,sm8150-refgen-regulator
+          - const: qcom,sdm845-refgen-regulator
+
+      - items:
+          - enum:
+              - qcom,sc7280-refgen-regulator
+              - qcom,sc8280xp-refgen-regulator
+              - qcom,sm6350-refgen-regulator
+              - qcom,sm6375-refgen-regulator
+              - qcom,sm8350-refgen-regulator
+          - const: qcom,sm8250-refgen-regulator
+
+      - enum:
+          - qcom,sdm845-refgen-regulator
+          - qcom,sm8250-refgen-regulator
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    regulator@162f000 {
+      compatible = "qcom,sm8250-refgen-regulator";
+      reg = <0x0162f000 0x84>;
+    };
+...