Create Event Gird subscription for Event Grid Topic NOT Event Grid System Topic

I have created an azurerm_eventgrid_topic using terraform, also using terraform I want to create a subscription to go with it. This can be done with the Ui on the menu sidebar under Entities. I have tried creating a * azurerm_eventgrid_event_subscription but this ends up creating a Azure event_grid_system_topic with the subscription. Is this functionality not possible through terraform at this time? Or what am I missing?