Welcome to the Universal Scalable Firmware project. The goal of the Universal Scalable Firmware project is to evolve the goodness of modularity to scale for IP FW development model, with emphasis on simplicity, scalability, debuggability, readability and determinism.
An overview of Universal Scalable Firmware project can be read here https://github.com/UniversalScalableFirmware/Introduction/blob/main/USF_Overview.pdf
The interface specification is at https://universalscalablefirmware.github.io/documentation/
The specification source is maintained in restructured text format and is available at https://github.com/UniversalScalableFirmware/documentation
Some sandbox implementations done as proof of concept of the Universal Scalable Firmware specification are available.
An POC implementation of Slim Bootloader https://github.com/UniversalScalableFirmware/slimbootloader
An POC implementation of coreboot https://github.com/UniversalScalableFirmware/coreboot
An POC implementation of UEFI Payload https://github.com/UniversalScalableFirmware/upld_test
An POC implementation of Linux Payload containing necessary patches to build a basic Linux payload https://github.com/UniversalScalableFirmware/linuxpayload
The pack_payload.py tool can be used to pack a normal payload image into the universal payload image format The clone_and_build_sbl_with_uefipayload.py tool could clone and build SBL + UEFI payload to have a quick try. https://github.com/UniversalScalableFirmware/tools