dt-bindings: mfd: Add ENE KB930 Embedded Controller binding

Add binding document for the ENE KB930 Embedded Controller.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/ene-kb930.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/ene-kb930.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ENE KB930 Embedded Controller bindings
+
+description: |
+  This binding describes the ENE KB930 Embedded Controller attached to an
+  I2C bus.
+
+maintainers:
+  - Dmitry Osipenko <digetx@gmail.com>
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - acer,a500-iconia-ec # Acer A500 Iconia tablet device
+      - const: ene,kb930
+  reg:
+    maxItems: 1
+
+  monitored-battery: true
+  power-supplies: true
+  system-power-controller: true
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    battery: battery-cell {
+      compatible = "simple-battery";
+      charge-full-design-microamp-hours = <3260000>;
+      energy-full-design-microwatt-hours = <24000000>;
+      operating-range-celsius = <0 40>;
+    };
+
+    mains: ac-adapter {
+      compatible = "gpio-charger";
+      charger-type = "mains";
+      gpios = <&gpio 125 0>;
+    };
+
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      embedded-controller@58 {
+        compatible = "acer,a500-iconia-ec", "ene,kb930";
+        reg = <0x58>;
+
+        system-power-controller;
+
+        monitored-battery = <&battery>;
+        power-supplies = <&mains>;
+      };
+    };
+
+...