Submission Only, Not Listening on 25.

[postfix]

I am setting up a postfix instance as submission only to compliment 
dovecot in imap mode.
Is there a way to turn off listening on port 25 and only have submission 
listen on 587?
I already know how to bind the submission service to 587 in the 
master.cf

I assume listening on 25 is controlled by inet_interfaces however i 
don't see anything in docs about specifying "nothing", its either all or 
a specific IP.

Is my only choice to allow postfix to bind to 25 and just firewall it 
off from the public? If possible id rather disable listening on 25 since 
its not being used.