configs: add readme.txt for the orangepipc defconfig

[Thomas: minor tweaks.]

Signed-off-by: Eelco Chaudron <echaudron@xiot.nl>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

board/orangepi/orangepipc/readme.txt

@@ -0,0 +1,33 @@
+OrangePi PC
+
+Intro
+=====
+
+This default configuration will allow you to start experimenting with the
+buildroot environment for the OrangePi PC. With the current configuration
+it will bring-up the board, and allow access trough the serial console.
+
+Unfortunately this boards processor is not yet supported by the
+mainline kernel, and therefore this default configuration is using a
+private Linux kernel repository based on 4.4-rc.
+
+How to build it
+===============
+
+Configure Buildroot:
+
+    $ make orangepipc_defconfig
+
+Compile everything and build the SD card image:
+
+    $ make
+
+How to write the SD card
+========================
+
+Once the build process is finished you will have an image called "sdcard.img"
+in the output/images/ directory.
+
+Copy the bootable "sdcard.img" onto an SD card with "dd":
+
+  $ sudo dd if=output/images/sdcard.img of=/dev/sdX