switch-to-visible-buffer

switch-to-visible-buffer is a variable defined in `window.el'.
Its value is

t

Documentation:
If non-nil, allow switching to an already visible buffer.
If this variable is non-nil, `switch-to-prev-buffer' and
`switch-to-next-buffer' may switch to an already visible buffer
provided the buffer was shown before in the window specified as
argument to those functions. If this variable is nil,
`switch-to-prev-buffer' and `switch-to-next-buffer' always try to
avoid switching to a buffer that is already visible in another
window on the same frame.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.