How do they shoot binocular scenes? Do they put two cameras in binoculars?
See this binocular vision from Ronin (1998):
As has been mentioned, the binocular "look" is just a mask.
It's also worth noting that if you're looking through binoculars properly you will only see one circle.
They don't, it's a fixed matte applied in post, these days with a simple 2D mask and some mild edge blurring. I'm reasonably certain nobody ever in the history of film and TV ever used anything optical to do that kind of shot.
"Binocular scenes" are shot as normal camera scenes. Then a "matte" or mask is added during post-production editing to simulate looking through binoculars.
Scenes where a character is looking something at the distance through binoculars are often enhanced by matting the screen with a double-circular frame. Recently, these scenes are filmed using a matte frame and a tint that is reminiscent of looking through a sniper scope.
Mattes cut holes in one clip to allow portions of another clip to show through. Mattes are used to create binocular and telescope point of view shots that were common in older movies and TV shows.