board: add a readme for Armadeus boards

Common readme.txt for all supported Armadeus boards.

Signed-off-by: Julien BOIBESSOT <julien.boibessot@armadeus.com>
[Thomas: minor tweaks in the readme.txt]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

board/armadeus/readme.txt

@@ -0,0 +1,89 @@
+Introduction
+============
+
+Armadeus APFxx are Systems On Module (SOM) based on Freescale/NXP i.MX
+processors associated with an FPGA (except on APF28). Non volatile
+data are stored in on-module NOR or NAND Flash, depending on the
+model. These SOM can be used on Armadeus development boards or with
+custom docking boards.
+
+Supported platforms
+===================
+
+Buildroot currently supports the following Armadeus platforms with the
+associated defconfigs:
+
+ * APF9328 SOM + devt boards -> armadeus_apf9328_defconfig
+ * APF27 SOM + devt board    -> armadeus_apf27_defconfig
+ * APF51 SOM + devt board    -> armadeus_apf51_defconfig
+ * APF28 SOM + devt board    -> armadeus_apf28_defconfig
+
+Vanilla Linux versions are preferred to Freescale's one in these
+configurations.
+
+How to build it
+===============
+
+Configure Buildroot
+-------------------
+
+Let's say you own an APFxx SOM with it's corresponding development
+board, all you have to do is:
+
+  $ make armadeus_apfxx_defconfig
+
+where "apfxx" is the version of your SOM.
+
+Launch build
+------------
+
+  $ make
+
+Result of the build
+-------------------
+
+When the build is finished, you will end up with:
+
+    output/images/
+    ├── imx**-apfxxdev.dtb	[1]
+    ├── rootfs.jffs2		[2]
+    ├── rootfs.tar
+    ├── rootfs.ubi		[2]
+    ├── rootfs.ubifs		[2]
+    └── uImage
+
+[1] Only if the kernel version used uses a Device Tree.
+[2] .ubi/.ubifs images are not available on APF9328 and replaced by a
+    .jffs2 one in this case.
+
+Building U-Boot is currently not supported in these configurations.
+
+Installation
+============
+
+You will require a serial connection to the board and a TFTP server on
+your Host PC. Assuming your server is configured for exporting
+/tftpboot/ directory, you will have to copy the generated images to
+it:
+
+  $ cp output/images/uImage /tftpboot/apfxx-linux.bin
+  $ cp output/images/*.dtb /tftpboot/
+  $ cp output/images/rootfs.ubi /tftpboot/apfxx-rootfs.ubi
+  $ cp output/images/rootfs.jffs2 /tftpboot/apfxx-rootfs.jffs2
+
+where "apfxx" is the version of your SOM, as used with _defconfigs.
+
+Then on your serial terminal, all you have to do is:
+
+* interrupt the boot process and access U-Boot console by pressing any
+  key when booting,
+* configure board and server IP addresses with "ipaddr" and "serverip"
+  environment variables,
+* if you want to update kernel:
+  BIOS > run update_kernel
+* if you want to update device tree:
+  BIOS > run update_dtb
+* if you want to update rootfs:
+  BIOS > run update_rootfs
+
+That's it !