regulator: Document bindings for max77826

Add device tree binding information for max77826 regulator driver.
Signed-off-by: Iskren Chernev <iskren.chernev@gmail.com>
Link: https://lore.kernel.org/r/20200414172250.2363235-3-iskren.chernev@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/maxim,max77826.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/maxim,max77826.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Maxim Integrated MAX77826 PMIC
+
+maintainers:
+  - Iskren Chernev <iskren.chernev@gmail.com>
+
+properties:
+  $nodename:
+    pattern: "pmic@[0-9a-f]{1,2}"
+  compatible:
+    enum:
+      - maxim,max77826
+
+  reg:
+    maxItems: 1
+
+  regulators:
+    type: object
+    allOf:
+      - $ref: regulator.yaml#
+    description: |
+      list of regulators provided by this controller, must be named
+      after their hardware counterparts LDO[1-15], BUCK and BUCKBOOST
+
+    patternProperties:
+      "^LDO([1-9]|1[0-5])$":
+        type: object
+        allOf:
+          - $ref: regulator.yaml#
+
+      "^BUCK|BUCKBOOST$":
+        type: object
+        allOf:
+          - $ref: regulator.yaml#
+
+      additionalProperties: false
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - regulators
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        pmic@69 {
+            compatible = "maxim,max77826";
+            reg = <0x69>;
+
+            regulators {
+                LDO2 {
+                    regulator-min-microvolt = <650000>;
+                    regulator-max-microvolt = <3587500>;
+                };
+            };
+       };
+     };
+...