doc/Host-tools-overview: tiffs-mkfs description updated The first version of tiffs-mkfs did not include a journal file in the created FFS, expecting the firmware to create it on first boot. All historical firmwares prior to a recent FC fix (2020-05) contain a bug in that code path, thus images made with the first version of tiffs-mkfs were only acceptable to very recent FC firmwares. tiffs-mkfs has now been extended to include an empty journal in the created FFS, thus the restriction of working with recent fw only has been lifted.