There is no formal yocto release from Freescale so far. But we are working to get it based on meta-fsl-arm from community.
I suggest to download, build and try the image, using meta-fsl-arm from community in meanwhile. This way you may get confortable with yocto *before* the formal release.
I´m planning a yocto traning showing the step-by-step for yocto building and some modification. It would be using latest stable branch (1.4 - dylan).
haitao, What kind of questions are you interested in?