The whole picture of accessory's firmware update?

I am a beginner as homeKit app developer, I was curious about how to excute an accessory firmware update? Apple just mentioned it as a custom service or something, no more detail.


I have 2 questions:


1.What prosess had to be made when updating? Such as where to download the firmware pack and how to get a notification that there is an new update? From apple or from our own? Is there any demo or apple recommendation to this?


2.Further more, when I notice there is an new firmware version, what should I do to execute this update service? Like I write an new value to one of the update service's characteristic?


Desprately expect some information about it, many thx!