Searches are way too much fun.
For a synopsis of a miniseries, Frank Miller's
The Dark Knight Returns has one as a sort of afterword. It's not what you mean, but it might be useful.
On an Amazon search, there's "Panel One: Comic Book Scripts By Top Writers" which seems like what you want. Seems there's a lot of different ways!
Here's another link, he writes them like scripts:
http//www.newsarama.com/general/WordsWordsWords/WWW03.htm
Writing them like scripts is probably the safest thing to do.