dt-bindings: regulator: Convert stm32 vrefbuf bindings to json-schema

Convert the STM32 regulator vrefbuf binding to DT schema format using json-schema
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
CC: Fabrice Gasnier <fabrice.gasnier@st.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20191122104536.20283-2-benjamin.gaignard@st.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/st,stm32-vrefbuf.txt

-STM32 VREFBUF - Voltage reference buffer
-
-Some STM32 devices embed a voltage reference buffer which can be used as
-voltage reference for ADCs, DACs and also as voltage reference for external
-components through the dedicated VREF+ pin.
-
-Required properties:
-- compatible:		Must be "st,stm32-vrefbuf".
-- reg:			Offset and length of VREFBUF register set.
-- clocks:		Must contain an entry for peripheral clock.
-
-Example:
-	vrefbuf: regulator@58003c00 {
-		compatible = "st,stm32-vrefbuf";
-		reg = <0x58003C00 0x8>;
-		clocks = <&rcc VREF_CK>;
-		regulator-min-microvolt = <1500000>;
-		regulator-max-microvolt = <2500000>;
-		vdda-supply = <&vdda>;
-	};

Documentation/devicetree/bindings/regulator/st,stm32-vrefbuf.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/st,stm32-vrefbuf.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: STMicroelectronics STM32 Voltage reference buffer bindings
+
+description: |
+  Some STM32 devices embed a voltage reference buffer which can be used as
+  voltage reference for ADCs, DACs and also as voltage reference for external
+  components through the dedicated VREF+ pin.
+
+maintainers:
+  - Fabrice Gasnier <fabrice.gasnier@st.com>
+
+allOf:
+  - $ref: "regulator.yaml#"
+
+properties:
+  compatible:
+    const: st,stm32-vrefbuf
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  vdda-supply:
+    description: phandle to the vdda input analog voltage.
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - vdda-supply
+
+examples:
+  - |
+    #include <dt-bindings/clock/stm32mp1-clks.h>
+    vrefbuf@50025000 {
+      compatible = "st,stm32-vrefbuf";
+      reg = <0x50025000 0x8>;
+      regulator-min-microvolt = <1500000>;
+      regulator-max-microvolt = <2500000>;
+      clocks = <&rcc VREF>;
+      vdda-supply = <&vdda>;
+    };
+
+...
+