window-at-side-list

window-at-side-list is a compiled Lisp function in `window.el'.

(window-at-side-list &optional FRAME SIDE)

Return list of all windows on SIDE of FRAME.
FRAME must be a live frame and defaults to the selected frame.
SIDE can be any of the symbols `left', `top', `right' or
`bottom'. The default value nil is handled like `bottom'.