Hi Okash,
Thanks for rebooting the conversation.
Out of the brainstorming from 1.5 yrs ago, we had this page published with an initial RFC proposal for LTSs: https://developer.trustedfirmware.org/w/tf_a/lts_proposal/
Worth mentioning that, in the meanwhile, the TF-M project has introduced the concept of Hotfix releases (which is a very lightweight process for backporting critical bug fix/security fixes only to the last available tagged release): https://tf-m-user-guide.trustedfirmware.org/docs/releases/release_process.ht...
I'm curious to hear others' opinion and interest (@Varun, @Raghu ?) to possibly revive this topic in either in a Tech Forum or at a project TSC/Board level.
Thanks Matteo