regulator: dt-bindings: mps,mp8859: convert to DT schema

Convert the Monolithic Power Systems MP8859 voltage regulator binding
from legacy text format to DT schema. This patch does not change any
functionality, the bindings remain the same.

Signed-off-by: Bhargav Joshi <rougueprince47@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260325230559.73527-1-rougueprince47@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/mp8859.txt

@@ -1,22 +0,0 @@
-Monolithic Power Systems MP8859 voltage regulator
-
-Required properties:
-- compatible: "mps,mp8859";
-- reg: I2C slave address.
-
-Optional subnode for regulator: "mp8859_dcdc", using common regulator
-bindings given in <Documentation/devicetree/bindings/regulator/regulator.txt>.
-
-Example:
-
-	mp8859: regulator@66 {
-		compatible = "mps,mp8859";
-		reg = <0x66>;
-		dc_12v: mp8859_dcdc {
-			regulator-name = "dc_12v";
-			regulator-min-microvolt = <12000000>;
-			regulator-max-microvolt = <12000000>;
-			regulator-boot-on;
-			regulator-always-on;
-		};
-	};

Documentation/devicetree/bindings/regulator/mps,mp8859.yaml

@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/mps,mp8859.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Monolithic Power Systems MP8859 Voltage Regulator
+
+maintainers:
+  - Markus Reichl <reichl@t-online.de>
+
+description:
+  The MP8859 is a synchronous, 4-switch, integrated buck-boost converter
+  capable of regulating the output voltage from 2.8V to 22V wide input voltage
+  range with high efficiency.
+
+properties:
+  compatible:
+    const: mps,mp8859
+
+  reg:
+    maxItems: 1
+
+  mp8859_dcdc:
+    $ref: /schemas/regulator/regulator.yaml#
+    type: object
+    description: DCDC regulator subnode
+    unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        regulator@66 {
+            compatible = "mps,mp8859";
+            reg = <0x66>;
+
+            mp8859_dcdc {
+                regulator-name = "dc_12v";
+                regulator-min-microvolt = <12000000>;
+                regulator-max-microvolt = <12000000>;
+                regulator-boot-on;
+                regulator-always-on;
+            };
+        };
+    };