Santa, we know, is an Elf. Or maybe he is a Maiar. At any rate he has been kicking around Eurasia for a really long time.
He is known in China as well as in the west of Eurasia. In China he is a jolly fat man who laughs a lot, and carries a bag full of sweets and goodies. He is called Pu Tai ("cloth sack"). He visits children on their birthdays and leaves them a present. He is especially fond of orphans. Pu Tai does not have reindeer in China and he is not associated specifically with midwinter. But he is the laughing god of luck.
He was made a Buddhist Bodhisattva (saint) and many Americans wrongly assume him to be the Buddha, Siddhārtha Gautama, the founder of the religion. He is not -- "buddha" just means "awakened" and there are lots of "buddhas". Pu Tai is the fat, jolly lucky one who brings presents to children -- the Chinese Santa Claus.
In the west, he was made a Christian saint -- St. Nicolas, or Saint Nick. Curiously, "Old Nick" is also a name for the Christian devil, whose iconography is derived from pre-Christian gods who wore horns. Santa has a definite "pagan" aura about him, and it's good bet he was carrying his sack full of goodies for children long before either Christianity or Buddhism existed.
Both religions decided he was something holy. Both grabbed him up for their own mythologies. But he just laughs and gives presents to children.