dt-bindings: power: supply: Add DT schema for richtek,rt5033-battery

The RT5033 PMIC provides a simple fuel gauge via I2C.
Add a DT schema to describe how to set it up in the device tree.

Note that although RT5033 is a MFD with lots of functionality
(also charger, regulator, LEDs, ...) the fuel gauge has a separate
I2C bus and is not part of the MFD.

Cc: Beomho Seo <beomho.seo@samsung.com>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Documentation/devicetree/bindings/power/supply/richtek,rt5033-battery.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/power/supply/richtek,rt5033-battery.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Richtek RT5033 PMIC Fuel Gauge
+
+maintainers:
+  - Stephan Gerhold <stephan@gerhold.net>
+
+allOf:
+  - $ref: power-supply.yaml#
+
+properties:
+  compatible:
+    const: richtek,rt5033-battery
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      battery@35 {
+        compatible = "richtek,rt5033-battery";
+        reg = <0x35>;
+      };
+    };
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      battery@35 {
+        compatible = "richtek,rt5033-battery";
+        reg = <0x35>;
+        interrupt-parent = <&msmgpio>;
+        interrupts = <121 IRQ_TYPE_EDGE_FALLING>;
+      };
+    };