directory-files-recursively

directory-files-recursively is a compiled Lisp function in `files.el'.

(directory-files-recursively DIR MATCH &optional INCLUDE-DIRECTORIES)

Return all files under DIR that have file names matching MATCH (a regexp).
This function works recursively. Files are returned in "depth first"
and alphabetical order.
If INCLUDE-DIRECTORIES, also include directories that have matching names.