@anshkapoor your model is too abstract. what do you mean by process1, process2, etc?
In BPMN terminology process is meant to the whole executable bpmn model. Are you trying to orchestrate multiple workflows through parent workflow?
So here, I’m guessing that various activities with in a single process you mentioned as process 1, process 2, etc instead of specifying/modelling task types like UserTask, ServiceTask, SendTask, Call Activity, etc. if its not the case then you might consider doing it by using call activity for orchestrating from parent workflow.
Suppose if you are referring process 1, process 2 to various bpmn activity types, then your requirement is achievable. Subprocess/event subprocess not required, can be done it with via exclusive gateway(1 path will be selected) or conditional sequence flows(more than 1 path can be selected based on criteria).