Six ways to sell through a partner instead of direct: referral, cloud marketplace, reseller, systems integrator, embedded technology, and OEM. Which one you need comes down to two things: who sets the price to the end customer, and who holds the end user contract.
Referral, reseller, distributor, or OEM. Sales usually names the deal before anyone maps the money, and that is how a reseller relationship ends up papered as a referral. Three questions sort it out: who pays you, who signs the end user, and who provisions the service.
A software referral agreement lives or dies on three things: which referrals you pay on, how and when you pay, and whether your partner and your own sales team can both understand it.