Keydash

You can dash through locked doors if you have the key for it and the correct positioning. To understand how this works, remember Link moves at 4 pixels per frame while dashing and locked doors have their unlocking trigger in front on them. The unlocking trigger is at a pixel precise position, and to activate this trigger, Link must land on the pixel on the way to the door so it opens before he reaches it.

So when dashing, Link must trigger the unlocking of the door and the door will open before colliding with it. If Link misses the trigger, he will bonk on the door and the dash's bonk will unlock the door. Look at the picture below, and it will probably make more sense.

The positions aren't right (in term of in-game position), but I think you will have a better view of how it works. The green path is a good path that will trigger the opening of the door so Link can pass through. The red path gets past the yellow line so that doesn't trigger the opening of the door before reaching it and therefore, this path will bonk the door

Luckily you don't have to worry about manually positioning yourself, the rooms are generally arranged on a grid where the pixel distance between all objects (walls, chests, torches, railings, pots, etc.) is a multiple of 4. So you can align Link with any object in the room before dashing towards the door, and you will have the correct positioning to pass through. Note that after you've aligned with an object, you must wait to input movement toward the door until AFTER you've started the dash charge animation. Moving before the animation will put you off of the object's coordinate, and you will most likely miss the keydash and bonk.