The file com.mysql.mysqld.plist should be placed in /Library/LaunchDaemons and the contents of the file should be as follows:
<?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>Program</key>
<string>/usr/local/mysql/bin/mysqld_safe</string>
<key>RunAtLoad</key>
<true/>
<key>UserName</key>
<string>mysql</string>
<key>WorkingDirectory</key>
<string>/usr/local/mysql</string>
</dict>
</plist>
