It’s called piebaldism. It’s caused in cats when melanistic cells (color causing cells) fail to migrate to all parts of the body during development. Such cats can have a wide variety of patterns from tuxedo cats to cow cats. This cat just has an unusual pattern.
A more common look:

https://en.wikipedia.org/wiki/Bicolor_cat
Chimerism causes left/right differences, not top to bottom.







Has that been suggested?