dt-bindings: rtc: Convert snps,dw-apb-timer to DT schema

Modern device tree bindings are supposed to be created as YAML-files
in accordance with DT schema. This commit replaces Synopsys DW Timer
legacy bare text binding with YAML file. As before the binding file
states that the corresponding dts node is supposed to be compatible
with generic DW APB Timer indicated by the "snps,dw-apb-timer"
compatible string and to provide a mandatory registers memory range,
one timer interrupt, either reference clock source or a fixed clock
rate value. It may also have an optional APB bus reference clock
phandle specified.

Signed-off-by: Serge Semin <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Cc: Alexey Malahov <[e-mail]>
Cc: Thomas Bogendoerfer <[e-mail]>
Cc: Paul Burton <[e-mail]>
Cc: Ralf Baechle <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Daniel Lezcano <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: [e-mail]
Signed-off-by: Daniel Lezcano <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/rtc/dw-apb.txt

···
-* Designware APB timer
-
-Required properties:
-- compatible: One of:
- 	"snps,dw-apb-timer"
-	"snps,dw-apb-timer-sp" <DEPRECATED>
-	"snps,dw-apb-timer-osc" <DEPRECATED>
-- reg: physical base address of the controller and length of memory mapped
-  region.
-- interrupts: IRQ line for the timer.
-- either clocks+clock-names or clock-frequency properties
-
-Optional properties:
-- clocks	: list of clock specifiers, corresponding to entries in
-		  the clock-names property;
-- clock-names	: should contain "timer" and "pclk" entries, matching entries
-		  in the clocks property.
-- clock-frequency: The frequency in HZ of the timer.
-- clock-freq: For backwards compatibility with picoxcell
-
-If using the clock specifiers, the pclk clock is optional, as not all
-systems may use one.
-
-
-Example:
-	timer@ffe00000 {
-		compatible = "snps,dw-apb-timer";
-		interrupts = <0 170 4>;
-		reg = <0xffe00000 0x1000>;
-		clocks = <&timer_clk>, <&timer_pclk>;
-		clock-names = "timer", "pclk";
-	};

Documentation/devicetree/bindings/rtc/snps,dw-apb-timer.yaml

···
+# SPDX-License-Identifier: GPL-2.0-only
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/snps,dw-apb-timer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Synopsys DesignWare APB Timer
+
+maintainers:
+  - Daniel Lezcano <[e-mail]>
+
+properties:
+  compatible:
+    oneOf:
+      - const: snps,dw-apb-timer
+      - enum:
+          - snps,dw-apb-timer-sp
+          - snps,dw-apb-timer-osc
+        deprecated: true
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    minItems: 1
+    items:
+       - description: Timer ticks reference clock source
+       - description: APB interface clock source
+
+  clock-names:
+    minItems: 1
+    items:
+      - const: timer
+      - const: pclk
+
+  clock-frequency: true
+
+  clock-freq:
+    $ref: "/schemas/types.yaml#/definitions/uint32"
+    description: |
+      Has the same meaning as the 'clock-frequency' property - timer clock
+      frequency in HZ, but is defined only for the backwards compatibility
+      with the picoxcell platform.
+
+unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+oneOf:
+  - required:
+      - clocks
+      - clock-names
+  - required:
+      - clock-frequency
+  - required:
+      - clock-freq
+
+examples:
+  - |
+    timer@ffe00000 {
+      compatible = "snps,dw-apb-timer";
+      interrupts = <0 170 4>;
+      reg = <0xffe00000 0x1000>;
+      clocks = <&timer_clk>, <&timer_pclk>;
+      clock-names = "timer", "pclk";
+    };
+  - |
+    timer@ffe00000 {
+      compatible = "snps,dw-apb-timer";
+      interrupts = <0 170 4>;
+      reg = <0xffe00000 0x1000>;
+      clocks = <&timer_clk>;
+      clock-names = "timer";
+    };
+  - |
+    timer@ffe00000 {
+      compatible = "snps,dw-apb-timer";
+      interrupts = <0 170 4>;
+      reg = <0xffe00000 0x1000>;
+      clock-frequency = <25000000>;
+    };
+...