root path custumized

Hello, I have configured my DNS CNAME: * .mydomain.com

Is this possible with nginx?

If the url does not have a sub domain use this root: /var/www/mydomain.com
If the url has www redirect to without www (that I already did)
If the url has the subdomain system (system.mydomain.com) use this root: /var/www/system
If the url has any other subdomain (company.mydomain.com or ong.mydomain.com) use this root: /var/www/companies

That's possible?

Thank you