Irish spotting is the often-seen pattern in for instance border collies, mantled great danes and basenjis.
Basically, the dog will have white feet, chest (not rarely with a neck collar) and
usually tailtip, with or without head markings. This gene has not been mapped, in fact, it appears to be dominant in some breeds and recessive in others so it's debated if it may actually be several different genes that cause similar
colour patterns in different breeds. It can be hard to tell where the border between piebald and
irish spotting goes in some dogs.
In bully breeds, it is not rare to see more white on the head and less on the tail and legs than in most other breeds.
Welsh corgi cardigan with irish spotting