regulator: add document bindings for sy8827n

Add device tree binding information for sy8827n regulator driver.
Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Link: https://lore.kernel.org/r/20200702171335.59f5e79b@xhacker.debianSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/silergy,sy8827n.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/silergy,sy8827n.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: silergy sy8827n PMIC
+
+maintainers:
+  - Jisheng Zhang <jszhang@kernel.org>
+
+properties:
+  compatible:
+    enum:
+      - silergy,sy8827n
+
+  reg:
+    maxItems: 1
+
+  enable-gpios:
+    description: GPIO to enable/disable the regulator.
+    maxItems: 1
+
+  silergy,vsel-state-high:
+    type: boolean
+    description:
+      Indicates if the VSEL pin is set to high.
+      If this property is missing, assume the VSEL pin is set to low.
+
+required:
+  - compatible
+  - reg
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        regulator@60 {
+          compatible = "silergy,sy8827n";
+          reg = <0x60>;
+        };
+    };
+
+...