Raspberry PI 3 - initial newb

[Da Rock]

Ok, so I got my hands on a RPi3 knowing that things aren't probably 
going to work straight off. Never worked with arm before, but trying to 
move towards the "future" :) rather than keep buying laptops. Haven't 
had much success with qemu as yet, and so thought hardware might be 
better and more fulfilling anyway. And they finally came in stock 
locally as well, so grabbed it while I could.

Booted raspbian straight off to get a handle on what control should look 
like, and got a nice little system with a rainbow icon in the corner 
(?). Grabbed the output from dmesg and such and kept a copy on my laptop.

My next research was to try building freebsd for arm/rpi3. Got current 
(10.x wouldn't do it) and built a distribution for arm64. So far so good 
- cross compile works fine with clang. (Remember, complete newb with 
cross compiling, arm, all that - worked on x86 only)

I then looked at the booting process, and u-boot. Sounds like a 
mindfield.... fun. Also came across crotchet, which as I understand has 
all this scripted, but for my purposes I need to actually understand the 
steps rather than have the script do it for me at this stage. So not 
real helpful at this point - if someone could point out the steps taken 
would be good.

So I then checked out the 10.3 rpi img from the FreeBSD downloads, and 
tried booting. NG. All I get is a rainbow test screen. Same with a 
11-current version too.

I post this here so I can get some pointers and advice on how to 
continue in my research and possibly getting my rpi3 to run.

It looks to me that the u-boot is grabbing the wrong address and so not 
booting the imgs properly.

Question: if the u-boot use loader to boot, then does that mean that 
once set there is no need to rebuild all as such - a kernel change can 
be initiated without hiccup? In other words, u-boot and loader stay in 
place, but nearly all can change around that?

I'm also noting the FDT, and I have the actual dtb file for the rpi3, 
but how would I use it? Am I right in assuming the file is platform 
neutral, and so will work for linux and FreeBSD?

Is there any good tutorials on using u-boot and configuring it correctly?

And the main reason why I could never get qemu to work with arm was it 
kept asking for a kernel file - is that meant to be the u-boot file then?

Cheers