Balanced parentheses

Write balanced(text) that returns True if every ( in text is closed by a later ) in the right order, and False otherwise. Only round brackets count; every other character, including [ and {, is ignored.

balanced("(a + b) * (c)")  ->  True
balanced("(()")            ->  False
balanced("())(")           ->  False
balanced("")               ->  True

def balanced(text):
    stack = []
    for ch in text:
        ...
    return ...