dt-bindings: arm: sp810: convert to DT schema

The Arm SP810 IP is a "system controller", providing clocks, timer and a
watchdog.

Convert the DT binding to DT schema, to allow automatic validation.

The existing .txt binding described all properties as required, but the
assigned-clock* and clock-output-names are actually not (from a hardware
perspective). The only existing driver I could find (in Linux) doesn't
require them either, so drop those properties from the "required" list.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220506140533.3566431-4-andre.przywara@arm.com

Documentation/devicetree/bindings/arm/sp810.txt

-SP810 System Controller
------------------------
-
-Required properties:
-
-- compatible:	standard compatible string for a Primecell peripheral,
-		see Documentation/devicetree/bindings/arm/primecell.yaml
-		for more details
-		should be: "arm,sp810", "arm,primecell"
-
-- reg:		standard registers property, physical address and size
-		of the control registers
-
-- clock-names:	from the common clock bindings, for more details see
-		Documentation/devicetree/bindings/clock/clock-bindings.txt;
-		should be: "refclk", "timclk", "apb_pclk"
-
-- clocks:	from the common clock bindings, phandle and clock
-		specifier pairs for the entries of clock-names property
-
-- #clock-cells: from the common clock bindings;
-		should be: <1>
-
-- clock-output-names: from the common clock bindings;
-		should be: "timerclken0", "timerclken1", "timerclken2", "timerclken3"
-
-- assigned-clocks: from the common clock binding;
-		should be: clock specifier for each output clock of this
-		provider node
-
-- assigned-clock-parents: from the common clock binding;
-		should be: phandle of input clock listed in clocks
-		property with the highest frequency
-
-Example:
-	v2m_sysctl: sysctl@20000 {
-		compatible = "arm,sp810", "arm,primecell";
-		reg = <0x020000 0x1000>;
-		clocks = <&v2m_refclk32khz>, <&v2m_refclk1mhz>, <&smbclk>;
-		clock-names = "refclk", "timclk", "apb_pclk";
-		#clock-cells = <1>;
-		clock-output-names = "timerclken0", "timerclken1", "timerclken2", "timerclken3";
-		assigned-clocks = <&v2m_sysctl 0>, <&v2m_sysctl 1>, <&v2m_sysctl 3>, <&v2m_sysctl 3>;
-		assigned-clock-parents = <&v2m_refclk1mhz>, <&v2m_refclk1mhz>, <&v2m_refclk1mhz>, <&v2m_refclk1mhz>;
-
-	};

Documentation/devicetree/bindings/arm/sp810.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/sp810.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ARM Versatile Express SP810 System Controller bindings
+
+maintainers:
+  - Andre Przywara <andre.przywara@arm.com>
+
+description:
+  The Arm SP810 system controller provides clocks, timers and a watchdog.
+
+# We need a select here so we don't match all nodes with 'arm,primecell'
+select:
+  properties:
+    compatible:
+      contains:
+        const: arm,sp810
+  required:
+    - compatible
+
+properties:
+  compatible:
+    items:
+      - const: arm,sp810
+      - const: arm,primecell
+
+  reg:
+    maxItems: 1
+
+  clock-names:
+    items:
+      - const: refclk
+      - const: timclk
+      - const: apb_pclk
+
+  clocks:
+    items:
+      - description: reference clock
+      - description: timer clock
+      - description: APB register access clock
+
+  "#clock-cells":
+    const: 1
+
+  clock-output-names:
+    maxItems: 4
+
+  assigned-clocks:
+    maxItems: 4
+
+  assigned-clock-parents:
+    maxItems: 4
+
+additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+  - "#clock-cells"
+
+examples:
+  - |
+    sysctl@20000 {
+        compatible = "arm,sp810", "arm,primecell";
+        reg = <0x020000 0x1000>;
+        clocks = <&v2m_refclk32khz>, <&v2m_refclk1mhz>, <&smbclk>;
+        clock-names = "refclk", "timclk", "apb_pclk";
+        #clock-cells = <1>;
+        clock-output-names = "timerclken0", "timerclken1",
+                             "timerclken2", "timerclken3";
+        assigned-clocks = <&v2m_sysctl 0>, <&v2m_sysctl 1>,
+                          <&v2m_sysctl 3>, <&v2m_sysctl 3>;
+        assigned-clock-parents = <&v2m_refclk1mhz>, <&v2m_refclk1mhz>,
+                                 <&v2m_refclk1mhz>, <&v2m_refclk1mhz>;
+    };