Change the premise a little, and you'll have a more interesting lore with more possibilities.
Everything is better with nanites!
Most of the inhabitants don't know it, but they can know it, because they have the same nanites in their bodies. Summoners, magicians, wizards, enchanters, witches, warlocks, alchemists, everyone is unwittingly a magical being.
The gods themselves, who exist as entities networked in all the nanites in all the creatures in the world, made it that way so that they can keep their status as gods, but they might as well have the same human origins. As such, becoming more in touch with your nanites is the same as having better control of your nanites
At the highest level of nanite control, you can be a god yourself. Or worse, the gods will turn you into a subservient demon if you try to enter their domain.
In the case of demons, they are also just subject to the reality-bending rules of self-made gods.
Demons can be summoned by magic words, which the gods can "hear" by reading the vibrations of your own larynx, since they have nanites there, like having a mic in your own throat.
Some demons can be summoned by writing pentagrams or runes, which the gods "see" by reading the images coming into your eyes, since they have nanites there. Think of QR code recognition, but with your own eyes.
Others can be summoned by sheer will, or intense emotions, or some combination of ideas, since gods can read your thoughts with nanites that read every firing of every neuron. You can be very afraid of something, and a certain adrenaline and heart-rate threshold will let a demon materialize before your very eyes... as the very thing you fear!. It can work with other emotions.
Better yet, some artifacts contain a specific set of nanites that require specific sets of instructions to unlock its utility functions, like it has to be powered by blood, with which the owner-determining function uses the DNA or the blood-type in that blood so that it only authenticates royal blood.
Since gods have access to your brain, they can override sensory functions and simulate real-world sensations with virtual ones and voila! You're in a catatonic state, trapped in a virtual reality, a nightmare, a hell. You can even mix real-world sensations with virtual ones and confuse your inhabitants to unfathomable levels of hallucination and madness.
Similarly, other demons can be ordered to possess people by letting a demon take over the conscious utilities of that person, essentially letting that demon wear that human body.
With nanites, you can rewrite reality with imagination. Combine some of the above, and you get some really complex magic systems that most readers will never ever question.
NOTE: Just call nanites as something else, like quantum mana, or anything related to magitek. Also, explain it in a more mystical tone that readers will have no idea what they're in for.
P.S.: I've had this idea for more than a decade, but I don't have the time to work out a masterpiece, so go ahead live my life for me.