dt-bindings: rtc: Split loongson,ls2x-rtc into SoC-based compatibles

Move Loongson RTC bindings from trivial-rtc.yaml into loongson,rtc.yaml.

The architectures associated with this driver use the built-in DTB, so
we can just drop the compatible(rtc-ls2x) with wildcards.
Also, soc-based compatible is more accurate for hardware differences
between chips.
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/1b0bb443bd74647c17b7902f3d719700f81a1dba.1685693501.git.zhoubinbin@loongson.cnSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/loongson,rtc.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/loongson,rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Loongson Real-Time Clock
+
+description:
+  The Loongson family chips use an on-chip counter 0 (Time Of Year
+  counter) as the RTC.
+
+maintainers:
+  - Binbin Zhou <zhoubinbin@loongson.cn>
+
+allOf:
+  - $ref: rtc.yaml#
+
+properties:
+  compatible:
+    oneOf:
+      - enum:
+          - loongson,ls1b-rtc
+          - loongson,ls1c-rtc
+          - loongson,ls7a-rtc
+          - loongson,ls2k1000-rtc
+      - items:
+          - enum:
+              - loongson,ls2k2000-rtc
+              - loongson,ls2k0500-rtc
+          - const: loongson,ls7a-rtc
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    rtc@1fe27800 {
+        compatible = "loongson,ls2k1000-rtc";
+        reg = <0x1fe27800 0x100>;
+
+        interrupt-parent = <&liointc1>;
+        interrupts = <8 IRQ_TYPE_LEVEL_HIGH>;
+    };
+
+...

Documentation/devicetree/bindings/rtc/trivial-rtc.yaml

@@ -47,8 +47,6 @@ properties:
       - isil,isl1218
       # Intersil ISL12022 Real-time Clock
       - isil,isl12022
-      # Loongson-2K Socs/LS7A bridge Real-time Clock
-      - loongson,ls2x-rtc
       # Real Time Clock Module with I2C-Bus
       - microcrystal,rv3029
       # Real Time Clock