images and isolinux directories

[Jerry Williams]

I have searched and searched and there is a lot of noise on the internet
about pieces and parts about the files in theses directories.

I have found short how to's on how to change them some.

But I have yet to find how and from what they are created in the first
place.  

Normal rpm's have src.rpm's

Is there a src.rpm for these?

Is there documentation on how to create them?

Please point me in the right direction.
Thanks!