Add documentation for Ariane FPGA platform

Signed-off-by: Panagiotis Peristerakis <perister@ics.forth.gr>

docs/platform/ariane-fpga.md

@@ -0,0 +1,37 @@
+Ariane FPGA SoC Platform
+==========================
+Ariane is a 6-stage, single issue, in-order CPU which implements the 64-bit RISC-V instruction set.
+The Ariane FPGA development platform is based on FPGA FPGA SoC(which currently supports only  Genesys 2 board) and is capable
+of running Linux.
+ The FPGA SoC currently contains the following peripherals:
+- DDR3 memory controller
+- SPI controller to conncet to an SDCard
+- Ethernet controller
+- JTAG port (see debugging section below)
+- Bootrom containing zero stage bootloader and device tree.
+
+To build platform specific library and firmwares, provide the
+*PLATFORM=ariane-fpga* parameter to the top level `make` command.
+
+Platform Options
+----------------
+
+The *Ariane FPGA* platform does not have any platform-specific
+options.
+
+Building Ariane FPGA Platform
+-----------------------------
+**Linux Kernel Payload**
+
+
+```
+make PLATFORM=ariane-fpga FW_PAYLOAD_PATH=<linux_build_directory>/arch/riscv/boot/Image
+```
+
+Booting Ariane FPGA Platform
+-----------------------------
+
+**Linux Kernel Payload**
+
+As Linux kernel image is embedded in the OpenSBI firmware binary, Ariane will directly
+boot into Linux directly after powered on.