dt-bindings: soc: microchip: sparx5-cpu-syscon: Move to dedicated schema

microchip,sparx5-cpu-syscon is not a simple syscon device - it has
children and implements simple-mfd compatible - thus it should be fully
documented in its own binding.

Reviewed-by: Rob Herring (Arm) <[e-mail]>
Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

Documentation/devicetree/bindings/mfd/syscon.yaml

···
               - mediatek,mt8173-pctl-a-syscfg
               - mediatek,mt8365-syscfg
               - microchip,lan966x-cpu-syscon
-              - microchip,sparx5-cpu-syscon
               - mstar,msc313-pmsleep
               - nuvoton,ma35d1-sys
               - nuvoton,wpcm450-shm

Documentation/devicetree/bindings/soc/microchip/microchip,sparx5-cpu-syscon.yaml

···
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/soc/microchip/microchip,sparx5-cpu-syscon.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip Sparx5 CPU Syscon
+
+maintainers:
+  - Lars Povlsen <[e-mail]>
+
+properties:
+  compatible:
+    items:
+      - const: microchip,sparx5-cpu-syscon
+      - const: syscon
+      - const: simple-mfd
+
+  reg:
+    maxItems: 1
+
+  mux-controller:
+    $ref: /schemas/mux/reg-mux.yaml#
+
+required:
+  - compatible
+  - reg
+  - mux-controller
+
+additionalProperties: false
+
+examples:
+  - |
+    soc {
+        #address-cells = <2>;
+        #size-cells = <1>;
+
+        syscon@600000000 {
+            compatible = "microchip,sparx5-cpu-syscon", "syscon",
+                         "simple-mfd";
+            reg = <0x6 0x00000000 0xd0>;
+
+            mux: mux-controller {
+                compatible = "mmio-mux";
+                #mux-control-cells = <1>;
+                mux-reg-masks = <0x88 0xf0>;
+            };
+        };
+    };