dt-bindings: pinctrl: spacemit: add syscon property

In order to access the protected IO power domain registers, a valid
unlock sequence must be performed by writing the required keys to the
AIB Secure Access Register (ASAR).

The ASAR register resides within the APBC register address space.
A corresponding syscon property is added to allow the pinctrl driver
to access this register.

Signed-off-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Linus Walleij <linusw@kernel.org>

Author: TroyMitchell911

Documentation/devicetree/bindings/pinctrl/spacemit,k1-pinctrl.yaml

@@ -32,6 +32,10 @@ properties:
   resets:
     maxItems: 1
 
+  spacemit,apbc:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description: Phandle to syscon that access the protected register
+
 patternProperties:
   '-cfg$':
     type: object
@@ -138,6 +142,7 @@ examples:
             clocks = <&syscon_apbc 42>,
                      <&syscon_apbc 94>;
             clock-names = "func", "bus";
+            spacemit,apbc = <&syscon_apbc>;
 
             uart0_2_cfg: uart0-2-cfg {
                 uart0-2-pins {