[PATCH 4/6] dt-bindings: watchdog: renesas: Document `renesas,r9a09g057-syscon-wdt-errorrst` property

[Prabhakar]

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

The RZ/V2H(P) CPG block includes Error Reset Registers (CPG_ERROR_RSTm).
A system reset is triggered in response to error interrupt factors, and
the corresponding bit is set in the CPG_ERROR_RSTm register. These
registers can be utilized by various IP blocks as needed.

In the event of a watchdog overflow or underflow, a system reset is issued,
and the CPG_ERROR_RST2[0/1/2/3] bits are set depending on the watchdog in
use: CM33 = 0, CA55 = 1, CR8_0 = 2, CR8_1 = 3. For the watchdog driver to
determine and report the current boot status, it needs to read the
CPG_ERROR_RST2[0/1/2/3]bits and provide this information to the user upon
request.

To facilitate this operation, add `renesas,r9a09g057-syscon-wdt-errorrst`
property to the WDT node, which maps to the `syscon` CPG node, enabling
retrieval of the necessary information. For example:

    wdt1: watchdog@14400000 {
        compatible = "renesas,r9a09g057-wdt";
        renesas,r9a09g057-syscon-wdt-errorrst = <&cpg 0xb40 1>;
        ...
    };

The `renesas,r9a09g057-syscon-wdt-errorrst` property consists of three
cells:
1. The first cell is a phandle to the CPG node.
2. The second cell specifies the offset of the CPG_ERROR_RSTm register
   within the SYSCON.
3. The third cell indicates the specific bit within the CPG_ERROR_RSTm
   register.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
---
 .../bindings/watchdog/renesas,wdt.yaml          | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml b/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml
index 29ada89fdcdc..8d29f5f1be7e 100644
--- a/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml
+++ b/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml
@@ -112,6 +112,19 @@ properties:
 
   timeout-sec: true
 
+  renesas,r9a09g057-syscon-wdt-errorrst:
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    description:
+      The first cell is a phandle to the SYSCON entry required to obtain
+      the current boot status. The second cell specifies the CPG_ERROR_RSTm
+      register offset within the SYSCON, and the third cell indicates the
+      bit within the CPG_ERROR_RSTm register.
+    items:
+      - items:
+          - description: Phandle to the CPG node
+          - description: The CPG_ERROR_RSTm register offset
+          - description: The bit within CPG_ERROR_RSTm register of interest
+
 required:
   - compatible
   - reg
@@ -182,7 +195,11 @@ allOf:
       properties:
         interrupts: false
         interrupt-names: false
+      required:
+        - renesas,r9a09g057-syscon-wdt-errorrst
     else:
+      properties:
+        renesas,r9a09g057-syscon-wdt-errorrst: false
       required:
         - interrupts
 
-- 
2.43.0