It doesn't make sense that you'd treat it differently. Patch policies are just that... policies. Meaning that they'll stage patches ahead of time and will execute on schedule. The SMP does not need to be online and available for your clients to perform their work provided the schedule and payload policies have been configured far enough in advance for the clients to obtain their required information.
That said, I have ALL of my SMP servers and services patching in the same group/schedule as 100 other servers in our environment.
What makes you believe that you have to treat your SMP differently?