spi: dw: Add AMD Pensando Elba SoC SPI Controller

The AMD Pensando Elba SoC has integrated the DW APB SPI Controller
Signed-off-by: Brad Larson <blarson@amd.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/20230410184526.15990-5-blarson@amd.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml

@@ -37,6 +37,17 @@ allOf:
     else:
       required:
         - interrupts
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: amd,pensando-elba-spi
+    then:
+      required:
+        - amd,pensando-elba-syscon
+    else:
+      properties:
+        amd,pensando-elba-syscon: false
 
 properties:
   compatible:
@@ -63,6 +74,8 @@ properties:
         const: intel,keembay-ssi
       - description: Intel Thunder Bay SPI Controller
         const: intel,thunderbay-ssi
+      - description: AMD Pensando Elba SoC SPI Controller
+        const: amd,pensando-elba-spi
       - description: Baikal-T1 SPI Controller
         const: baikal,bt1-ssi
       - description: Baikal-T1 System Boot SPI Controller
@@ -136,6 +149,12 @@ properties:
       of the designware controller, and the upper limit is also subject to
       controller configuration.
 
+  amd,pensando-elba-syscon:
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    description:
+      Block address to control SPI chip-selects. The Elba SoC system controller
+      provides an interface to override the native DWC SSI CS control.
+
 patternProperties:
   "^.*@[0-9a-f]+$":
     type: object