Trusted Firmware-A project is still currently hosted and developed under GitHub:

https://github.com/ARM-software/arm-trusted-firmware

All the relevant documentation is still available at https://github.com/ARM-software/arm-trusted-firmware/blob/master/readme.rst and into the specific docs folder https://github.com/ARM-software/arm-trusted-firmware/tree/master/docs

All the content will be soon migrated here.