Finding non-smoking restaurants in Japan

In Japan, some restaurants and cafes have designated smoking seating (separate areas or floors), some are fully non-smoking and some are fully smoking.

A few times we’ve found a nice looking restaurant online or in the hotel advertising, only to find out it was fully smoking.

When searching for a place to eat online (or checking an advertised or recommended one), how do I filter out smoking venues?

Google Maps lists restaurants but doesn’t explicitly say whether they are smoking or not.