Docker is not honoring configuration to listen on tcp socket

I would like to configure docker to listen on port tcp://0.0.0.0:2375.
I have tried different configuration options like /etc/docker/daemon.json and /etc/default/docker with
DOCKER_OPTS="--host unix:///var/run/docker.sock --host tcp://0.0.0.0:2375 --dns 1.2.3.4"
but docker will never use the tcp settings.

The only way I have found that works is to change /etc/systemd/system/multi-user.target.wants/docker.service
BUT this file is replaced every time there is a new version.

What is the correct way to configure docker to listen on 'tcp://0.0.0.0:2375' and specify dns???