dt-bindings: rtc: Add TI K3 RTC description

This adds the documentation for the devicetree bindings of the Texas
Instruments RTC modules on K3 family of SoCs such as AM62x SoCs or
newer.
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220623170808.20998-2-nm@ti.com

Documentation/devicetree/bindings/rtc/ti,k3-rtc.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/ti,k3-rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Texas Instruments K3 Real Time Clock
+
+maintainers:
+  - Nishanth Menon <nm@ti.com>
+
+description: |
+  This RTC appears in the AM62x family of SoCs.
+
+allOf:
+  - $ref: "rtc.yaml#"
+
+properties:
+  compatible:
+    enum:
+      - ti,am62-rtc
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: VBUS Interface clock
+      - description: 32k Clock source (external or internal).
+
+  clock-names:
+    items:
+      - const: vbus
+      - const: osc32k
+
+  power-domains:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    rtc@2b1f0000 {
+        compatible = "ti,am62-rtc";
+        reg = <0x2b1f0000 0x100>;
+        interrupts = <GIC_SPI 100 IRQ_TYPE_LEVEL_HIGH>;
+        power-domains = <&bar 0>;
+        clocks = <&foo 0>, <&foo 1>;
+        clock-names = "vbus", "osc32k";
+        wakeup-source;
+    };