dt-bindings: fpga: Add bindings for ZynqMP fpga driver

Add documentation to describe Xilinx ZynqMP fpga driver
bindings.
Signed-off-by: NNava kishore Manne <nava.manne@xilinx.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Acked-by: NAlan Tull <atull@kernel.org>
Acked-by: NMoritz Fischer <mdf@kernel.org>
Signed-off-by: NMichal Simek <michal.simek@xilinx.com>

Documentation/devicetree/bindings/fpga/xlnx,zynqmp-pcap-fpga.txt

+Devicetree bindings for Zynq Ultrascale MPSoC FPGA Manager.
+The ZynqMP SoC uses the PCAP (Processor configuration Port) to configure the
+Programmable Logic (PL). The configuration uses  the firmware interface.
+
+Required properties:
+- compatible: should contain "xlnx,zynqmp-pcap-fpga"
+
+Example for full FPGA configuration:
+
+	fpga-region0 {
+		compatible = "fpga-region";
+		fpga-mgr = <&zynqmp_pcap>;
+		#address-cells = <0x1>;
+		#size-cells = <0x1>;
+	};
+
+	firmware {
+		zynqmp_firmware: zynqmp-firmware {
+			compatible = "xlnx,zynqmp-firmware";
+			method = "smc";
+			zynqmp_pcap: pcap {
+				compatible = "xlnx,zynqmp-pcap-fpga";
+			};
+		};
+	};