dt-bindings: timer: Add Broadcom's BCMBCA timers

BCA is a big set / family of Broadcom devices sharing multiple hardware
blocks. One of them is timer that actually exists in two versions. It's
a part of TWD MFD block.

Add binding for it so SoCs can be properly described. Linux (and
probably any other OS) doesn't really seem to need a driver for it. it
may be needed for bootloaders (e.g. U-Boot) though. Especially for SoCs
with CPUs other than Cortex-A9 (which contains arch timers).
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20221028115353.13881-1-zajec5@gmail.com

Documentation/devicetree/bindings/mfd/brcm,twd.yaml

@@ -36,6 +36,9 @@ properties:
     const: 1
 
 patternProperties:
+  '^timer@[a-f0-9]+$':
+    $ref: /schemas/timer/brcm,bcmbca-timer.yaml
+
   '^watchdog@[a-f0-9]+$':
     $ref: /schemas/watchdog/brcm,bcm7038-wdt.yaml
 
@@ -54,6 +57,11 @@ examples:
         #address-cells = <1>;
         #size-cells = <1>;
 
+        timer@0 {
+            compatible = "brcm,bcm63138-timer";
+            reg = <0x0 0x28>;
+        };
+
         watchdog@28 {
             compatible = "brcm,bcm7038-wdt";
             reg = <0x28 0x8>;

Documentation/devicetree/bindings/timer/brcm,bcmbca-timer.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/timer/brcm,bcmbca-timer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom Broadband SoC timer
+
+maintainers:
+  - Rafał Miłecki <rafal@milecki.pl>
+
+properties:
+  compatible:
+    oneOf:
+      - const: brcm,bcm6345-timer
+        description: >
+          An old block with 3 timers.
+
+          It can be found in BCM6345, BCM6838 and BCM63268.
+      - const: brcm,bcm63138-timer
+        description: >
+          Updated block with 4 timers and control regs at the beginning.
+
+          It can be found in newer SoCs, e.g. BCM63138, BCM63148, BCM63381,
+          BCM68360, BCM6848, BCM6858, BCM4908.
+
+  reg:
+    maxItems: 1
+
+additionalProperties: false
+
+required:
+  - reg
+
+examples:
+  - |
+    timer@fffe0200 {
+      compatible = "brcm,bcm6345-timer";
+      reg = <0xfffe0200 0x1c>;
+    };