Because the vendor should provide an SDK for development?
It's fine if the vendor's image is based on Yocto, but you should still be able to download something from them with instructions.
That's literally what Yocto builds for you.
you should still be able to download something from them with instructions.
As an example, here's Freescale/NXP's github with their Yocto recipes. It was not "nuked from orbit" on the purchase.
https://github.com/Freescale/fsl-community-bsp-platform
And a sample build guide:
http://www.nxp.com/assets/documents/data/en/release-notes/IM...
