[CentOS] linux-3.10.0-514.el7.tar.xz - process of creation

I try to create own patch for kernel, and I look in process of
generation binary rpm file.
As I can see, for creation binary package, rpmbuild doesn't uses any set
of patches and doesn't uses file of original (vanilla) version of
kernel. Instead it, I see some xz archive of compressed tree of kernel
probably with all changes (linux-3.10.0-514.el7.tar.xz). How and where I
can find process of creation of this archive and to see separately all
set of patches? I want to remove some changes and add own.

Many thanks to all, who have such info and can give link on process or
link on documentations of process of creation of this archive.

best regards, Andrei

upwork.link