Autostart MySQL Server on Mac OS X Yosemite/El Capitan

@dcc was very close. This is how MySQL autostarts again on Yosemite:

The com.mysql.mysql.plist in /Library/LaunchDaemons:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>KeepAlive</key>
    <true/>
    <key>Label</key>
    <string>com.mysql.mysqld</string>
    <key>ProgramArguments</key>
    <array>
    <string>/usr/local/mysql/bin/mysqld_safe</string>
    <string>--user=mysql</string>
    </array>
  </dict>
</plist>

Additionally I've changed the permissions based on this answer

sudo chown root:wheel /Library/LaunchDaemons/com.mysql.mysql.plist
sudo chmod 644 /Library/LaunchDaemons/com.mysql.mysql.plist

Finally I run this command

sudo launchctl load -w /Library/LaunchDaemons/com.mysql.mysql.plist

If you have any addition please share below!

I followed @Xavers directions and upon trying to execute the command

sudo launchctl load -w /Library/LaunchDaemons/com.mysql.mysql.plist

was given the error:

/Library/LaunchDaemons/com.mysql.mysql.plist: Invalid property list

After scratching my head for a minute I found that removing the DOCTYPE DTD declaration at the top made the error go away and upon restart mySQL server is, indeed, running.

So, my XML looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<plist version="1.0">
  <dict>
    <key>KeepAlive</key>
    <true/>
    <key>Label</key>
    <string>com.mysql.mysqld</string>
    <key>ProgramArguments</key>
    <array>
    <string>/usr/local/mysql/bin/mysqld_safe</string>
    <string>--user=mysql</string>
    </array>
  </dict>
</plist>