[Clfs-support] sub-level kernel patch in clfs recipes question

[lux-integ]

Greetings,

Can someone explain the reason for the use of  'sub-level' kernel patches' 
for example:-
xzcat ../patch-3.14.21.xz | patch -Np1 -i -

mentioned in clfs-builds :-
http://clfs.org/view/git/x86_64/cross-tools/linux-headers.html
and here
http://clfs.org/view/git/x86_64/final-system/linux-headers.html
and here
http://clfs.org/view/git/x86_64/bootable/kernel.html


( I am using linux-3.18.5 and the correspending patch-3.18.5.xz )           
For the first time I  applied  the required patch  in all three places   and 
when  I came to compile the kernel  -make failed 
Bit it compiled fine  without  the patch.

( I did  repeat runs  and executed 'make mrproper'  after applying the patch ) 
and make failed  every time.)

Comments welcomed.


Sincerely
luxInteg