dt-bindings: rtc: pcf2123: convert to YAML

Convert the existing txt binding to the preferred YAML format.

The pcf2123 node may contain SPI settings such as spi-cs-high and
spi-max-frequency, which keeps it from being added to the trivial-rtc
binding with its current definition. Add a reference to
spi-peripheral-props.yaml to account for that.

The "interrupts" property was missing in the binding although it is
already supported. Add the missing property in the new binding.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230907-topic-pcf2123_yaml-v2-1-ea87a8e12190@gmail.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/nxp,pcf2123.yaml

@@ -0,0 +1,47 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/nxp,pcf2123.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NXP PCF2123 SPI Real Time Clock
+
+maintainers:
+  - Javier Carrasco <javier.carrasco.cruz@gmail.com>
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+  - $ref: rtc.yaml#
+
+properties:
+  compatible:
+    enum:
+      - nxp,pcf2123
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        rtc@3 {
+            compatible = "nxp,pcf2123";
+            reg = <3>;
+            interrupts = <GIC_SPI 130 IRQ_TYPE_LEVEL_LOW>;
+            spi-cs-high;
+        };
+    };
+...