Can you cast banishment on yourself from a non-native plane, as a way of returning to your native plane?
From the Basic Rules, p.80:
If a spell targets a creature of your choice, you can choose yourself, unless the creature must be hostile or specifically a creature other than you. If you are in the area of effect of a spell you cast, you can target yourself.
It appears that, as long as you can see yourself, you're a legal target for banishment since it does not specify that it has to be a creature other than you.
If you were already on your own native plane and the spell successfully affected you, then at this point you would be sent to a harmless demiplane in which you would be incapacitated, immediately breaking concentration and returning you to the point at which you cast it upon yourself.
However, the incapacitation effect is not specified for creatures not on their native plane at the time of their banishment; You should be able to continue maintaining concentration for the remaining minute after sending yourself there, at which point it would be 'permanent'. (This may be a neat 'dodging' mechanic for if your environment suddenly becomes temporarily dangerous- banish yourself, and release concentration before it becomes 'permanent')
It may be worth houseruling that you have to succeed on a basic concentration check (constitution saving throw, DC 10) for shifting yourself via a method probably meant for banishing others, but that's not necessary by RAW.