dt-bindings: mfd: Add Renesas R2A11302FT PMIC

This PMIC is referenced in upstream DTs for the Renesas Lager and
Koelsch boards. Sadly, there is no documentation available. This minimal
binding description states the facts that we do know.

Fixes:
arch/arm/boot/dts/renesas/r8a7790-lager.dtb: /soc/spi@e6e10000/pmic@0: failed to match any schema with compatible: ['renesas,r2a11302ft']
arch/arm/boot/dts/renesas/r8a7791-koelsch.dtb: /soc/spi@e6e20000/pmic@0: failed to match any schema with compatible: ['renesas,r2a11302ft']

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20251010094734.10487-2-wsa+renesas@sang-engineering.com
Signed-off-by: Lee Jones <lee@kernel.org>

Documentation/devicetree/bindings/mfd/renesas,r2a11302ft.yaml

@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/renesas,r2a11302ft.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Renesas R2A11302FT Power Supply ICs for R-Car
+
+maintainers:
+  - Wolfram Sang <wsa+renesas@sang-engineering.com>
+
+description: |
+  The Renesas R2A11302FT PMIC is used with Renesas R-Car Gen1/Gen2
+  based SoCs.
+
+  FIXME: The binding is incomplete and resembles the information gathered
+  so far.
+
+properties:
+  compatible:
+    const: renesas,r2a11302ft
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 6000000
+
+  spi-cpol: true
+
+  spi-cpha: true
+
+required:
+  - compatible
+  - reg
+  - spi-cpol
+  - spi-cpha
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        pmic@0 {
+            compatible = "renesas,r2a11302ft";
+            reg = <0>;
+            spi-max-frequency = <6000000>;
+            spi-cpol;
+            spi-cpha;
+        };
+    };
+...