Lib and Src directory

Hey, newbie question here:

What is the interpretation between the src/ and lib/ directory?
For example, I see files like integrity.c or verity.c etc. Are these files also files written for the cryptsetup project,
or do these contain the same code that can be found in the linux kernel /drivers/md/dm-integrity.c for example?

I'm sorry if this doesn't make sense, but I don't fully understand how much and which code is intertwined with the code written in the Linux kernel drivers section.

Thanks!