Which keymap was found with key-binding?

[Martin Stone Davis]

The function `key-binding' returns the definition of a key by looking 
through the minor-mode map, local, and then global keymaps (I guess).  I 
would like a function that returns the keymap itself.  That is, given a 
key, it looks through the appropriate keymaps.  When it finds a matching 
keymap it return that keymap.

Does such a thing already exist?