dt/bindings: Add binding for Versatile system registers

Add binding for Versatile board system registers found in the FPGA of the
Versatile/AB and Versatile/PB boards.

Signed-off-by: Rob Herring <[email protected]>
Cc: Pawel Moll <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Ian Campbell <[email protected]>
Cc: Kumar Gala <[email protected]>
Cc: [email protected]
Signed-off-by: Daniel Lezcano <[email protected]>

Author: robherring

Documentation/devicetree/bindings/arm/versatile-sysreg.txt

@@ -0,0 +1,10 @@
+ARM Versatile system registers
+--------------------------------------
+
+This is a system control registers block, providing multiple low level
+platform functions like board detection and identification, software
+interrupt generation, MMC and NOR Flash control etc.
+
+Required node properties:
+- compatible value : = "arm,versatile-sysreg", "syscon"
+- reg : physical base address and the size of the registers window