dt-bindings: regulator: Add bindings for Silicon Mitus SM5703 regulators

This patch adds device-tree bindings for regulators on Silicon Mitus
SM5703 MFD.
Signed-off-by: Markuss Broks <markuss.broks@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220423085319.483524-3-markuss.broks@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/siliconmitus,sm5703-regulator.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/siliconmitus,sm5703-regulator.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Silicon Mitus SM5703 multi function device regulators
+
+maintainers:
+  - Markuss Broks <markuss.broks@gmail.com>
+
+description: |
+  SM5703 regulators node should be a sub node of the SM5703 MFD node. See SM5703 MFD
+  bindings at Documentation/devicetree/bindings/mfd/siliconmitus,sm5703.yaml
+  Regulator nodes should be named as USBLDO_<number>, BUCK, VBUS, LDO_<number>.
+  The definition for each of these nodes is defined using the standard
+  binding for regulators at Documentation/devicetree/bindings/regulator/regulator.txt.
+
+properties:
+  buck:
+    type: object
+    $ref: regulators.yaml#
+    unevaluatedProperties: false
+    description:
+      Properties for the BUCK regulator.
+
+  vbus:
+    type: object
+    $ref: regulators.yaml#
+    unevaluatedProperties: false
+    description:
+      Properties for the VBUS regulator.
+
+patternProperties:
+  "^ldo[1-3]$":
+    type: object
+    $ref: regulators.yaml#
+    unevaluatedProperties: false
+    description:
+      Properties for single LDO regulator.
+
+  "^usbldo[1-2]$":
+    type: object
+    $ref: regulators.yaml#
+    unevaluatedProperties: false
+    description:
+      Properties for a single USBLDO regulator.
+
+additionalProperties: false