dt-bindings: rtc: rv3032: add RV-3032 bindings

Document the Microcrystal RV-3032 device tree bindings
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201013144110.1942218-2-alexandre.belloni@bootlin.com

Documentation/devicetree/bindings/rtc/microcrystal,rv3032.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/microcrystal,rv3032.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip RV-3032 RTC Device Tree Bindings
+
+allOf:
+  - $ref: "rtc.yaml#"
+
+maintainers:
+  - Alexandre Belloni <alexandre.belloni@bootlin.com>
+
+properties:
+  compatible:
+    const: microcrystal,rv3032
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  start-year: true
+
+  trickle-resistor-ohms:
+    enum:
+      - 1000
+      - 2000
+      - 7000
+      - 11000
+
+  trickle-voltage-millivolt:
+    enum:
+      - 1750
+      - 3000
+      - 4400
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        rtc@51 {
+            compatible = "microcrystal,rv3032";
+            reg = <0x51>;
+            status = "okay";
+            pinctrl-0 = <&rtc_nint_pins>;
+            interrupts-extended = <&gpio1 16 IRQ_TYPE_LEVEL_HIGH>;
+            trickle-resistor-ohms = <7000>;
+            trickle-voltage-millivolt = <1750>;
+        };
+    };
+
+...