Bruce Banner says in Avengers: Infinity War that Vision is composed of many layers when discussing how to destroy the Mind Stone. In those layers he includes himself.
Your mind is made of a complex construct of overlays. Jarvis, Ultron, Tony, me, the stone. All of them mixed together.
Is this some kind of metaphor or is there something else going on?
Maybe something happened between Avengers: Age of Ultron and Thor: Ragnarok?
Why each of the components Bruce mentioned are a part of Vision:
This is scene by the following dialogue from Avengers: Age of Ultron:
Bruce Banner: So, you want me to help you put JARVIS into this thing?
Tony Stark: No, of course not! I want to help you put JARVIS in this thing. [Banner shakes his head] We're out of my field here. You know bio-organics better than anyone.
Ultron itself was a construct of;
The brain patterns of Tony Stark and Bruce Banner. They were attempting to create an advanced Artificial Intelligence, capable of solely being able to protect the earth as a new version of the Iron Legion, now dubbed the Ultron program. They were unsuccessful however, and were only able to complete a sufficient enough A.I using a net of neurons they believed they were capable of reprogramming to achieve their goal. They were wrong.
Ultron went sentient and aimed to use the regeneration cradle, a machine that can sculpt organic matter, mixed with the magical alien metal vibranium, to give him more durable and adaptable properties to his new body, and then topped off with the actual artifact that helped finish his code, the powerful mind stone.. essentially turning his new body from an advanced being, into a God.
Then we have the final piece..
Jarvis: an intelligence program made presumably by Tony Stark, but perhaps there is more history to the program maybe involving Howard Stark, and others?, before Tony took over from his father. Maybe not, but in any circumstances we know Tony was definitely involved, even if it was by himself. We know that Jarvis is Just A Rather Very Intelligent System, and has handled Starks day to day, being in charge of Tony's mansion, his Iron Man suits, and Stark Tower, and not only that, but being able to do all of this independent from Starks control. The Jarvis program was also able to aide all of the Avengers on their various missions. It even tried to keep Ultron from accessing the larger Internet, in an attempt to quell its rage.
When Stark and Banner obtained the resurrection cradle from Ultron, they obtained the snythezoid body Ultron had created, powered by the Mind Stone, and with the Ultron program almost entirely installed. They then uploaded a refound JARVIS program, an entirely good structure, into the Ultron framework, and were then helped bring him to life with the power of Thor. An actual God.
So in reality, Vision is made up of:
-STARKS brain waves
-BRUCE BANNERS brain waves
-MIND STONE neuron patterns recoded Then the three of these melding and evolving with the knowledge of every piece of recorded information known on Earth, by us, or kept in secret, to create...
-ULTRON. and even though the ULTRON program evolves and becomes its own thing, it still retains these separate properties.
-VIBRANIUM and all its magical alien properties, mixed with organic material created by some of Earth's top scientists and engineers.
-The actual MIND STONE, and all of the knowledge and millenia spanning power it possesses.
-The power and life blood of ASGARD, MJLONIR,and THOR.
All of these things create Vision, and yet, once Vision has come into being, due to its intelligence, its networks, its power source, the properties of their unique build up of body and systems within it evolves at a rapid pace, and becomes something akin to a God.
