Hi Allan,
I have been reading u-boot documentation for last few weeks.
I hope it was fun :)
I am looking forward to configure & write my own u-boot for some board or CPU . I will be doing it first time.
Please suggest some existing board for which we have opensource U-boot software available, which are good for someone to start ?
This is a very broad question and without giving us more context like price range, expected features, CPU architecture, etc. it is very hard to answer.
An "objective" start however would be to look into boards.cfg in mainline to see what boards we support. If you have narrowed down your choice a little bit, I'm optimistic that people will then be glad to help find a local optimum amongst them.
I can study that & apply same concept to other Processors or boards. I will like to be an expert in u-boot porting.
TI sitara controllers or RPi(I have an Rpi) or some thing else ?
I am no expert on either one, but the Rpi is not an easy beast to tame. If you want to learn, I'd suggest looking for less complicated architectures that have been supported already for a while.
Best wishes Detlev