Multisite domain naming
i am new to wordpress multi-site. We are planning to have PaaS.
Internal subdomains i know can be possible to map. However can i use external subdomain via DNA (cname) to map?
for example
i know that subdomain.mydomain.com is possible but subdomain.notmydomain.com can be possible?
what can be the requirements/suggestions for such a setup in terms of hosting.
thank you.