dt-bindings: soc: cix: document the syscon on Sky1 SoC

There are two system control on Cix sky1 Soc. One is located in S0 domain,
and the other is located in S5 domain. The system control contains resets,
usb typeC and more. At this point, only the reset controller is embedded
as usb typeC uses it by phandle.

Signed-off-by: Gary Yang <gary.yang@cixtech.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

Documentation/devicetree/bindings/soc/cix/cix,sky1-system-control.yaml

@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/soc/cix/cix,sky1-system-control.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Cix Sky1 SoC system control register region
+
+maintainers:
+  - Gary Yang <gary.yang@cixtech.com>
+
+description:
+  An wide assortment of registers of the system controller on Sky1 SoC,
+  including resets, usb, wakeup sources and so on.
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - cix,sky1-system-control
+          - cix,sky1-s5-system-control
+      - const: syscon
+
+  reg:
+    maxItems: 1
+
+  '#reset-cells':
+    const: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    syscon@4160000 {
+      compatible = "cix,sky1-system-control", "syscon";
+      reg = <0x4160000 0x100>;
+      #reset-cells = <1>;
+    };