Why do you think jelly bean is SO easy to port ?

[Madarox]

ok since google announced jelly bean on 28th june,many phones started getting ports after.Even the nokia N9 ! Why wasn't it the same with ICS ? I know that JB is based on ICS but it's actually ICS with some modifications.

 

[Shadowriver]

I assume by annoucment you mean IO2011. Source been relesed when ICS been relesed which is November.

Also i belive there really not much issue with "porting" with any Android as long as you already got existing "port". Key element is Linux kernel which contains all the drivers and support for hardware, it's kernel is the one that supports hardware, Android is just a front end to it, Android does not interact with hardware direcly. Linux it self usally don't change dramatically to level that software running on it shadenly stop after new version (in matter of 3.0 update just was versioning policy change in Linux kernel project, theres no much change since 2.6.x), if something is not workign it usally need recompilation with new linux headers, also Linux never drops features it has, so as long you have working kernel for specific hardware it should handle any Android or else you got some odd drivers and Android don't know how to talk to them.