See instructions on oe-lite.org on how to get requirements for oe-lite.
Next, clone this repository:

oe clone git://oe-lite.org/bsp/raspberrypi.git

Change to the raspberrypi manifest directory:

cd raspberrypi

Now edit conf/local.conf. You can change PARALLEL_MAKE and SDK_CPU
to fit your needs.

Then you are ready to get a bootable SD-card:

oe bake bootfs rootfs 

wait a while for the building to complete.

Assuming sd-card reader is /dev/sdb (WARNING: be sure, the script does
not check if you got it wrong and disk will be erased!
./scripts/mk_sd.sh /dev/sdb tmp/images

TODO:
a recipe to setup config.txt to configure overclocking, hdmi, etc.
(I however just uses the serial console so I have not been in need for this yet)