README: update building/flashing docs

Signed-off-by: Ian Pozella <[email protected]>

Author: Ham22

README.md

@@ -1,45 +1,17 @@
 # Using u-boot on Creator (Ci40) Marduk platform
 
-### How to build/cross-compile for Ci40:
+## Toolchain setup
+If you are using the toolchain produced by OpenWrt you must setup the environment as explained
+[here](https://wiki.openwrt.org/doc/devel/crosscompile).
 
-	$ export CROSS_COMPILE=/path/to/mips-toolchain/mips-toolchain-prefix
-	$ make pistachio_marduk_defconfig
-	$ make
+For the MIPS official toolchain see
+[here](https://community.imgtec.com/developers/mips/tools/codescape-mips-sdk/download-codescape-mips-sdk-essentials/).
 
-This will generate u-boot-pistachio-nor.img
-
-Note: Using OpenWrt's toolchain toolchain-mipsel_mips32_gcc-5.2.0_musl-1.1.11 will require [this patch](http://lists.denx.de/pipermail/u-boot/2015-July/217911.html) to be applied.
-
-### How to flash on Ci40:
-
-1. [Load OpenWrt](https://github.com/IMGCreator/openwrt/blob/master-pistachio/README.md)
-
-2. Erase and write u-boot image on bootloader partition of Ci40
-
-		$ flashcp -v u-boot-pistachio-nor.img /dev/mtd0
-
-	Note: flashcp needs to be manually selected in OpneWrt menuconfig
+## Configure and build it
+	$ make CROSS_COMPILE=<toolchain-prefix> pistachio_marduk_defconfig
+	$ make CROSS_COMPILE=<toolchain-prefix>
 
-		Base system -> busybox -> Cutomize busybox options -> Miscellaneous Utilities -> flashcp
-
-3. Reboot
-
-		$ reboot
-
-	Once restarted the board, you should see the date when you have built the u-boot on the console as follows:
-
-		U-Boot SPL 2015.07-rc2 (Jun 14 2016 - 19:20:36)
-		
-		
-		U-Boot 2015.07-rc2 (Jun 14 2016 - 19:20:36 +0530)
-		
-		MIPS(interAptiv): IMG Pistachio 546MHz.
-		Model: IMG Marduk
-		DRAM:  256 MiB
-		NAND:  512 MiB
-		MMC:   Synopsys Mobile storage: 0
-		SF: Detected W25Q16CL with page size 256 Bytes, erase size 4 KiB, total 2 MiB
-
-This means your built u-boot image has been flashed properly on the board!!
+This will generate u-boot-pistachio-nor.img
 
-_Please be aware that you may brick the board if you flashed a wrong bootloader. Only way to re-cover back the board is to use Dedi-prog SF100 programmer to flash the pre-built bootloader again._
+## Flash it onto your Ci40
+See our [docs](https://docs.creatordev.io/ci40/guides/openwrt-platform/#flashing-u-boot-binary).