Vincent Zimmer of Intel has a new blog post, on UEFI’s EDK-II and Intel FSP (Firmware Support Package), and how the FSP works with the EDK-II. Good background, with lots of links.
https://firmware.intel.com/blog/open-source-platforms-edkii-using-intel-fsp
For more information on UEFI and FSP, also read the APress book, which Vincent is one of the authors:
https://firmwaresecurity.com/2015/05/09/book-review-embedded-firmware-solutions/