Thanks for the links. Though i am trying this kernel compilation thing after around 7-8 years.

Here is my understanding

@juiceme - I think that builds just the vmlinuz kernel (+modules etc). I am fine with that portion.

What about the rootfs ? Handset UX, x11, qt etc (and the connected launch/init scripts, homescreen et al.) ?

@halftux
I am still going through your links. From a cursory glance the docker/vmimage stuff seems they are for compiling meego apps/sdk Probably you meant the same when you said that it cannot build the full firmware image ? I may be wrong here (correct me).
searching for Sailfish - am not sure how much of it is related
The mer link looks more promising (though long back i saw it when to N900/n9 with mic/obs etc, need to read again i think).

There are some tizen links with mic, but obs replaced by gbs. Scratchbox seems like a dead project now, no one working on it. Need to check mer's scratchbox.

Will go through it. Thanks for the pointers.