[Buildroot] populating an initramfs

Hi All,

Forgive me in advance for asking a newb question.  I'm in the process
of converting from Yocto/OE.

I have the need to populate both an initramfs as well as a rootfs with
the contents of packages I build using buildroot.  What is the best
way to do this?   Should I create two separate projects, one for the
initramfs and one for the rootfs?  Or is there a way to select which
contents go in each and keep it all in the same project?

Thanks,

Dallas