[PATCH v2 2/3] dt-bindings: arm: stm32: allow TAMP nvram child node for syscon

[Patrice Chotard <patrice.chotard@foss.st.com>]

The STM32 TAMP node (compatible "st,stm32-tamp", "syscon", "simple-mfd")
exposes its backup registers through an nvram child node described by
nvmem/st,stm32-tamp-nvram.yaml. That requires the TAMP node to carry
"#address-cells", "#size-cells", "ranges" and an "nvram@..." child.

st,stm32-syscon.yaml uses "additionalProperties: false" and only allowed
reg/clocks/#clock-cells, so wiring the nvram provider into the DTSI made
"make dtbs_check" fail on every STM32MP TAMP node:

  tamp@5c00a000 (st,stm32-tamp): '#address-cells', '#size-cells',
  'nvram@5c00a100', 'ranges' do not match any of the regexes:
  '^pinctrl-[0-9]+$'

Allow the addressing properties and the nvram child, gated on the
st,stm32-tamp compatible so the other syscon variants stay strict.
"#size-cells" may be 1 or 2: the STM32MP21 soc bus uses two size cells
(an empty "ranges" requires the node to match its parent) while the
other STM32MP SoCs use one.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
---
 .../bindings/arm/stm32/st,stm32-syscon.yaml        | 30 ++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/Documentation/devicetree/bindings/arm/stm32/st,stm32-syscon.yaml b/Documentation/devicetree/bindings/arm/stm32/st,stm32-syscon.yaml
index 95d2319afe23..1aeb54867db2 100644
--- a/Documentation/devicetree/bindings/arm/stm32/st,stm32-syscon.yaml
+++ b/Documentation/devicetree/bindings/arm/stm32/st,stm32-syscon.yaml
@@ -39,6 +39,23 @@ properties:
   "#clock-cells":
     const: 0
 
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    enum: [1, 2]
+
+  ranges: true
+
+patternProperties:
+  "^nvram@[0-9a-f]+$":
+    type: object
+    description:
+      TAMP backup registers exposed as an NVMEM provider. See
+      nvmem/st,stm32-tamp-nvram.yaml.
+    required:
+      - compatible
+
 required:
   - compatible
   - reg
@@ -61,6 +78,19 @@ allOf:
     then:
       required:
         - "#clock-cells"
+  - if:
+      not:
+        properties:
+          compatible:
+            contains:
+              const: st,stm32-tamp
+    then:
+      properties:
+        "#address-cells": false
+        "#size-cells": false
+        ranges: false
+      patternProperties:
+        "^nvram@[0-9a-f]+$": false
 
 additionalProperties: false
 

-- 
2.43.0