dt-bindings: timers: sp-804: Convert to json-schema

This converts the DT binding documentation for the ARM SP-804 timer IP
over to json-schema.
Most properties are just carried over, the clocks property requirement
(either one or three clocks) is now formalised and enforced.
As the former binding didn't specify clock-names, and there is no
common name used by the existing DTs, I refrained from adding them in
detail (just allowing the property).
The requirement for the APB clock is enforced by the primecell binding
already.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20200828142018.43298-2-andre.przywara@arm.com
[robh: drop primecell.yaml]
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/timer/arm,sp804.txt

-ARM sp804 Dual Timers
----------------------------------------
-
-Required properties:
-- compatible: Should be "arm,sp804" & "arm,primecell"
-- interrupts: Should contain the list of Dual Timer interrupts. This is the
-	interrupt for timer 1 and timer 2. In the case of a single entry, it is
-	the combined interrupt or if "arm,sp804-has-irq" is present that
-	specifies which timer interrupt is connected.
-- reg: Should contain location and length for dual timer register.
-- clocks: clocks driving the dual timer hardware. This list should be 1 or 3
-	clocks.	With 3 clocks, the order is timer0 clock, timer1 clock,
-	apb_pclk. A single clock can also be specified if the same clock is
-	used for all clock inputs.
-
-Optional properties:
-- arm,sp804-has-irq = <#>: In the case of only 1 timer irq line connected, this
-	specifies if the irq connection is for timer 1 or timer 2. A value of 1
-	or 2 should be used.
-
-Example:
-
-	timer0: timer@fc800000 {
-		compatible = "arm,sp804", "arm,primecell";
-		reg = <0xfc800000 0x1000>;
-		interrupts = <0 0 4>, <0 1 4>;
-		clocks = <&timclk1 &timclk2 &pclk>;
-		clock-names = "timer1", "timer2", "apb_pclk";
-	};

Documentation/devicetree/bindings/timer/arm,sp804.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/timer/arm,sp804.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ARM sp804 Dual Timers
+
+maintainers:
+  - Haojian Zhuang <haojian.zhuang@linaro.org>
+
+description: |+
+  The Arm SP804 IP implements two independent timers, configurable for
+  16 or 32 bit operation and capable of running in one-shot, periodic, or
+  free-running mode. The input clock is shared, but can be gated and prescaled
+  independently for each timer.
+
+# Need a custom select here or 'arm,primecell' will match on lots of nodes
+select:
+  properties:
+    compatible:
+      contains:
+        const: arm,sp804
+  required:
+    - compatible
+
+properties:
+  compatible:
+    items:
+      - const: arm,sp804
+      - const: arm,primecell
+
+  interrupts:
+    description: |
+      If two interrupts are listed, those are the interrupts for timer
+      1 and 2, respectively. If there is only a single interrupt, it is
+      either a combined interrupt or the sole interrupt of one timer, as
+      specified by the "arm,sp804-has-irq" property.
+    minItems: 1
+    maxItems: 2
+
+  reg:
+    description: The physical base address of the SP804 IP.
+    maxItems: 1
+
+  clocks:
+    description: |
+      Clocks driving the dual timer hardware. This list should
+      be 1 or 3 clocks. With 3 clocks, the order is timer0 clock, timer1
+      clock, apb_pclk. A single clock can also be specified if the same
+      clock is used for all clock inputs.
+    oneOf:
+      - items:
+        - description: clock for timer 1
+        - description: clock for timer 2
+        - description: bus clock
+      - items:
+        - description: unified clock for both timers and the bus
+
+  clock-names: true
+    # The original binding did not specify any clock names, and there is no
+    # consistent naming used in the existing DTs. The primecell binding
+    # requires the "apb_pclk" name, so we need this property.
+    # Use "timer0clk", "timer1clk", "apb_pclk" for new DTs.
+
+  arm,sp804-has-irq:
+    description: If only one interrupt line is connected to the interrupt
+      controller, this property specifies which timer is connected to this
+      line.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 1
+    maximum: 2
+
+required:
+  - compatible
+  - interrupts
+  - reg
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    timer0: timer@fc800000 {
+        compatible = "arm,sp804", "arm,primecell";
+        reg = <0xfc800000 0x1000>;
+        interrupts = <0 0 4>, <0 1 4>;
+        clocks = <&timclk1>, <&timclk2>, <&pclk>;
+        clock-names = "timer1", "timer2", "apb_pclk";
+    };