dt-bindings: rtc: renesas,rzg3s-rtc: Document the Renesas RTCA-3 IP

Document the RTC IP (RTCA-3) available on the Renesas RZ/G3S SoC.
The RTC IP available on Renesas RZ/V2H is almost identical with the
one found on Renesas RZ/G3S (it misses the time capture functionality
which is not yet implemented on proposed driver). For this, added also a
generic compatible that will be used at the moment as fallback for both
RZ/G3S and RZ/V2H.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20241030110120.332802-5-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/renesas,rz-rtca3.yaml

@@ -0,0 +1,84 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/renesas,rz-rtca3.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Renesas RTCA-3 Real Time Clock
+
+maintainers:
+  - Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
+
+allOf:
+  - $ref: rtc.yaml#
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - renesas,r9a08g045-rtca3 # RZ/G3S
+      - const: renesas,rz-rtca3
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    items:
+      - description: Alarm interrupt
+      - description: Periodic interrupt
+      - description: Carry interrupt
+
+  interrupt-names:
+    items:
+      - const: alarm
+      - const: period
+      - const: carry
+
+  clocks:
+    items:
+      - description: RTC bus clock
+      - description: RTC counter clock
+
+  clock-names:
+    items:
+      - const: bus
+      - const: counter
+
+  power-domains:
+    maxItems: 1
+
+  resets:
+    items:
+      - description: VBATTB module reset
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-names
+  - clocks
+  - clock-names
+  - power-domains
+  - resets
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/r9a08g045-cpg.h>
+    #include <dt-bindings/clock/renesas,r9a08g045-vbattb.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    rtc@1004ec00 {
+        compatible = "renesas,r9a08g045-rtca3", "renesas,rz-rtca3";
+        reg = <0x1004ec00 0x400>;
+        interrupts = <GIC_SPI 315 IRQ_TYPE_LEVEL_HIGH>,
+                     <GIC_SPI 316 IRQ_TYPE_LEVEL_HIGH>,
+                     <GIC_SPI 317 IRQ_TYPE_LEVEL_HIGH>;
+        interrupt-names = "alarm", "period", "carry";
+        clocks = <&cpg CPG_MOD R9A08G045_VBAT_BCLK>, <&vbattclk VBATTB_VBATTCLK>;
+        clock-names = "bus", "counter";
+        power-domains = <&cpg>;
+        resets = <&cpg R9A08G045_VBAT_BRESETN>;
+    };