Laurie Jarlstrom of Intel has announced a documentation update to the UEFI Forum’s EDK II Specifications:
“Announcing the V1.25 and V1.26 updates to the EDK II Specifications. Go to the EDK II Specifications page to download the latest documentation.”
These are the specs beyond the UEFI Forum’s PI and UEFI specs, focused on development implementation details of Tianocore’s EDK-II.
https://github.com/tianocore/tianocore.github.io/wiki/EDK-II-Specifications
http://article.gmane.org/gmane.comp.bios.edk2.devel/6371