Sorry for disturbing (or for uploading wrong files).
I don't remember where I got them from, probably from a FTP server somewhere; they are for this phone for sure, or atleast for the medfield platform; I searched for a file for my ST-Ericsson SoC on my Samsung Galaxy S Advance and I found it on one of these tar.gz archives; a long time ago - Today, while checking this phone (and this thread), I remembered that I have those files, I uploaded them, maybe they could be useful for someone here...
Replying to my own post.
After looking a old backup on a old disk of my download server, this is where I originally found the packages, but I believe you already looked at them, didn't you?
This seems to be the original source from stock (and remember Intel is very open with Linux, I don't see why it would be different with Android). Instructions seems very basics, download 4.1.x source, copy sources from files, build with script on one of the vendor folders; debug.
Sorry for bothering if any of this is not useful at all.