regulator: dt-bindings: add documentation for s2mpu05-pmic regulators

S2MPU05 is a PMIC found in Exynos7870 devices, which controls voltage
regulators (21 LDOs and 5 BUCKs). Provide documentation for devicetree
definitions, regulator naming patterns, etc.

Signed-off-by: Kaustabh Chakraborty <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

Documentation/devicetree/bindings/regulator/samsung,s2mpu05.yaml

···
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/samsung,s2mpu05.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Samsung S2MPU05 Power Management IC regulators
+
+maintainers:
+  - Kaustabh Chakraborty <[e-mail]>
+
+description: |
+  This is a part of device tree bindings for S2M and S5M family of Power
+  Management IC (PMIC).
+
+  The S2MPU05 provides buck and LDO regulators.
+
+  See also Documentation/devicetree/bindings/mfd/samsung,s2mps11.yaml for
+  additional information and example.
+
+patternProperties:
+  # 21 LDOs
+  "^ldo([1-9]|10|2[5-9]|3[0-5])$":
+    type: object
+    $ref: regulator.yaml#
+    unevaluatedProperties: false
+    description:
+      Properties for single LDO regulator.
+
+      LDOs 11-24 are used for CP, and they're left unimplemented due to lack
+      of documentation on these regulators.
+
+    required:
+      - regulator-name
+
+  # 5 bucks
+  "^buck[1-5]$":
+    type: object
+    $ref: regulator.yaml#
+    unevaluatedProperties: false
+    description:
+      Properties for single buck regulator.
+
+    required:
+      - regulator-name
+
+additionalProperties: false