dt-binding: mfd: Document canaan,k210-sysctl bindings

Document the device tree bindings of the Canaan Kendryte K210 SoC
system controller driver in
Documentation/devicetree/bindings/mfd/canaan,k210-sysctl.yaml.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

Documentation/devicetree/bindings/mfd/canaan,k210-sysctl.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/canaan,k210-sysctl.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Canaan Kendryte K210 System Controller Device Tree Bindings
+
+maintainers:
+  - Damien Le Moal <damien.lemoal@wdc.com>
+
+description:
+  Canaan Inc. Kendryte K210 SoC system controller which provides a
+  register map for controlling the clocks, reset signals and pin power
+  domains of the SoC.
+
+properties:
+  compatible:
+    items:
+      - const: canaan,k210-sysctl
+      - const: syscon
+      - const: simple-mfd
+
+  clocks:
+    maxItems: 1
+    description:
+      System controller Advanced Power Bus (APB) interface clock source.
+
+  clock-names:
+    items:
+      - const: pclk
+
+  reg:
+    maxItems: 1
+
+  clock-controller:
+    # Child node
+    type: object
+    $ref: "../clock/canaan,k210-clk.yaml"
+    description:
+      Clock controller for the SoC clocks. This child node definition
+      should follow the bindings specified in
+      Documentation/devicetree/bindings/clock/canaan,k210-clk.yaml.
+
+  reset-controller:
+    # Child node
+    type: object
+    $ref: "../reset/canaan,k210-rst.yaml"
+    description:
+      Reset controller for the SoC. This child node definition
+      should follow the bindings specified in
+      Documentation/devicetree/bindings/reset/canaan,k210-rst.yaml.
+
+  syscon-reboot:
+    # Child node
+    type: object
+    $ref: "../power/reset/syscon-reboot.yaml"
+    description:
+      Reboot method for the SoC. This child node definition
+      should follow the bindings specified in
+      Documentation/devicetree/bindings/power/reset/syscon-reboot.yaml.
+
+required:
+  - compatible
+  - clocks
+  - reg
+  - clock-controller
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/k210-clk.h>
+    #include <dt-bindings/reset/k210-rst.h>
+
+    clocks {
+      in0: oscllator {
+        compatible = "fixed-clock";
+        #clock-cells = <0>;
+        clock-frequency = <26000000>;
+      };
+    };
+
+    sysctl: syscon@50440000 {
+      compatible = "canaan,k210-sysctl",
+                   "syscon", "simple-mfd";
+      reg = <0x50440000 0x100>;
+      clocks = <&sysclk K210_CLK_APB1>;
+      clock-names = "pclk";
+
+      sysclk: clock-controller {
+        #clock-cells = <1>;
+        compatible = "canaan,k210-clk";
+        clocks = <&in0>;
+      };
+
+      sysrst: reset-controller {
+        compatible = "canaan,k210-rst";
+        #reset-cells = <1>;
+      };
+
+      reboot: syscon-reboot {
+        compatible = "syscon-reboot";
+        regmap = <&sysctl>;
+        offset = <48>;
+        mask = <1>;
+        value = <1>;
+      };
+    };