This is a short overview on how to completely remove any old mysql server installs in OSX and upgrade to MariaDB without conflicts. Things can get a bit weird when you have various old installs of MySQL server floating around, and utilizing homebrew to install and upgrade MariaDB as a drop in replacement for MySQL has worked well, especially if you're used to managing MySQL installs via yum in linux.
Backup all of your current databases with mysqldump
This isn't a tutorial on backups, and there are many ways to do it. You should know how to backup your data anyway. For this example, we'll do a full backup of our InnoDB databases.