Nokia shows how Android updates are processed before they are rolled out in their finished version.
Nokia has made a nice and clear graphical overview of how an update is made ready for their mobile phones. There is a long way from start to finish.
Nokia is proud of their choice of Android One and they are certainly not afraid to show it. If you are not sure what Android One is, read more here . In short, it is Android that Google itself thinks it should be. In addition, Android One promises 3 years of security updates and 2 years of software updates.
In the overview you can see how an update starts with the chipset manufacturers, and finally ends with the consumer. See here: