I am not sure if this tradition is anywhere but here in the States. In fact, it was nothing I had ever heard of until my kids were young and I received one as a gift.
As I was unpacking ornaments the other day, I came across our Santa Key. It was so much fun when they were little to ceremoniously hang it off the frog door knocker we had at our old house and throw reindeer food off the porch on Christmas Eve while the chocolate chip cookies for Santa were baking.
WAIT! You mean you guys haven't heard of reindeer food either?
OH no. I'd better find you a recipe. Big day is coming and Santa's reindeer might be very hungry.