"Error in query (1030): Got error 168 from storage engine" when creating table
apparmor (and selinux) provide additional access controls beyond permissions that can cause these permission denied (13) errors. This occurs generally on systems where data or log files differ from the default.

With apparmor you would add to the bottom of /etc/apparmor.d/local/usr.sbin.mysqld:

/media/sdc/mysql/ r,
/media/sdc/mysql/** rwk, 


And then reload the apparmor service:

service apparmor reload 


If it was selinux:

semanage fcontext -a -t mysqld_db_t "/media/sdc/mysql(/.*)?"
restorecon -Rv /media/sdc/mysql