customize-face-other-window is an interactive autoloaded compiled Lisp function in `cus-edit.el'.

(customize-face-other-window &optional FACE)

Show customization buffer for face FACE in other window.
If FACE is actually a face-alias, customize the face it is aliased to.

Interactively, when point is on text which has a face specified,
suggest to customize that face, if it's customizable.