[RFC PATCH 5/9] dt-bindings: watchdog: renesas,r9a09g057-wdt: Add SYS syscon support

[Prabhakar]

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

On the Renesas RZ/T2H SoC, the Watchdog Timer Control Register (WDTDCR)
resides within the System Controller (SYS) block rather than the WDT
address space itself.

Previously, this was handled by including a second register range in the
"reg" property. However, this is architecturally incorrect as the SYS
block consists of two distinct regions (0x80290000 and 0x81290000) that
contain registers for multiple peripheral blocks.

Now that the SYS driver provides a unified syscon regmap, introduce the
"renesas,sys" phandle-array property to allow the WDT driver to
access its control register via the system controller.

Mark the use of a second "reg" entry as deprecated in favor of the
new phandle-array approach for SoCs that require WDTDCR access.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
---
 .../watchdog/renesas,r9a09g057-wdt.yaml       | 29 +++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/watchdog/renesas,r9a09g057-wdt.yaml b/Documentation/devicetree/bindings/watchdog/renesas,r9a09g057-wdt.yaml
index 099200c4f136..2f32c7401def 100644
--- a/Documentation/devicetree/bindings/watchdog/renesas,r9a09g057-wdt.yaml
+++ b/Documentation/devicetree/bindings/watchdog/renesas,r9a09g057-wdt.yaml
@@ -48,6 +48,17 @@ properties:
   resets:
     maxItems: 1
 
+  renesas,sys:
+    description:
+      System controller registers control the start/stop of the WDT, and halt debug.
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    items:
+      - items:
+          - description: phandle to system controller
+          - description: watchdog IP instance index
+            minimum: 0
+            maximum: 5
+
   timeout-sec: true
 
 required:
@@ -73,15 +84,29 @@ allOf:
           minItems: 2
         clock-names:
           minItems: 2
+        renesas,sys: false
     else:
       properties:
         clocks:
           maxItems: 1
         clock-names:
           maxItems: 1
-        reg:
-          minItems: 2
         resets: false
+      allOf:
+        - if:
+            required:
+              - renesas,sys
+          then:
+            properties:
+              reg:
+                maxItems: 1
+          else:
+            properties:
+              reg:
+                description: Deprecated. Use renesas,sys to pass the offset
+                             of WDTDCR register instead.
+                minItems: 2
+                deprecated: true
 
 additionalProperties: false
 
-- 
2.54.0