dt-bindings: power: supply: Document Mitsumi MM8013 fuel gauge

The Mitsumi MM8013 is an I2C fuel gauge for Li-Ion cells. The partial
datasheet is available at [1]. Add bindings for this chip.

[1] https://www.mitsumi.co.jp/latest-M/Catalog/pdf/battery_mm_8013_e.pdfReviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20230621-topic-mm8013-v4-2-975aecd173ed@linaro.orgSigned-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Documentation/devicetree/bindings/power/supply/mitsumi,mm8013.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/power/supply/mitsumi,mm8013.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Mitsumi MM8013 fuel gauge
+
+maintainers:
+  - Konrad Dybcio <konradybcio@kernel.org>
+
+allOf:
+  - $ref: power-supply.yaml#
+
+properties:
+  compatible:
+    const: mitsumi,mm8013
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      fuel-gauge@55 {
+        compatible = "mitsumi,mm8013";
+        reg = <0x55>;
+      };
+    };