Terminal 1
ssh -L /tmp/mysqltun.sock:/var/run/mysqld/mysqld.sock remote.mysql-server.tld -N
Terminal 2
mysql -h localhost -p -u root -S /tmp/mysqltun.sock
Or
ssh -L 3306:/var/run/mysqld/mysqld.sock remote.mysql-server.tld -N
Terminal 2
mysql -h 127.0.0.1 -p -u root --protocol SOCKET