realtek: timer driver: documentation

Provide some helpful information about the devicetree configuration of
our new driver

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
[correct compatible order in examples]
Signed-off-by: Sander Vanheule <sander@svanheule.net>

target/linux/realtek/files-5.10/Documentation/devicetree/bindings/realtek,otto-timer.yaml

@@ -0,0 +1,85 @@
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/timer/realtek,rtl8300-timer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Realtek Timer Device Tree Bindings
+
+maintainers:
+  - Markus Stockhausen <markus.stockhausen@gmx.de>
+
+description: |
+  The Realtek SOCs of the RTL83XX and RTL93XX series have at least 5 known
+  timers with corresponding interrupt lines . Their speed is derived from the
+  Lexra Bus (LXB) by dividers. Each timer has a block of 4 control registers in
+  the address range 0xb800xxxx with following start offsets.
+
+  RTL83XX: 0x3100, 0x3110, 0x3120, 0x3130, 0x3140
+  RTL93XX: 0x3200, 0x3210, 0x3220, 0x3230, 0x3240
+ 
+properties:
+  compatible:
+    items:
+      - enum:
+        - realtek,rtl8380-timer
+        - realtek,rtl8390-timer
+        - realtek,rtl9300-timer
+      - const: realtek,otto-timer
+
+  reg:
+    minItems: 5
+    maxItems: 5
+    description:
+      List of timer register addresses.
+
+  interrupts:
+    minItems: 5
+    maxItems: 5
+    description:
+      List of timer interrupts.
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    timer0: timer@3100 {
+      compatible = "realtek,rtl8380-timer", "realtek,otto-timer";
+      reg = <0x3100 0x10>, <0x3110 0x10>, <0x3120 0x10>,
+            <0x3130 0x10>, <0x3140 0x10>;
+
+      interrupt-parent = <&intc>;
+      interrupts = <29 4>, <28 4>, <17 4>, <16 4>, <15 4>;
+      clocks = <&ccu CLK_LXB>;
+    };
+  - |
+    timer0: timer@3100 {
+      compatible = "realtek,rtl8390-timer", "realtek,otto-timer";
+      reg = <0x3100 0x10>, <0x3110 0x10>, <0x3120 0x10>,
+            <0x3130 0x10>, <0x3140 0x10>;
+
+      interrupt-parent = <&intc>;
+      interrupts = <29 4>, <28 4>, <17 4>, <16 4>, <15 4>;
+      clocks = <&ccu CLK_LXB>;
+    };
+  - |
+    timer0: timer@3200 {
+      compatible = "realtek,rtl9300-timer", "realtek,otto-timer";
+      reg = <0x3200 0x10>, <0x3210 0x10>, <0x3220 0x10>,
+            <0x3230 0x10>, <0x3240 0x10>;
+
+      interrupt-parent = <&intc>;
+      interrupts = <7 4>, <8 4>, <9 4>, <10 4>, <11 4>;
+      clocks = <&ccu CLK_LXB>;
+    };
+
+...