Yes, upstreaming RTEMS is definitely a great idea! I know of (at least) two different projects that are interested in your RTEMS work
![Smile :)](./images/smilies/icon_e_smile.gif)
Stay tuned with regards to how to submit patches to the tool chain. I am not the right person for that, but hopefully Jeremyandr Ola can help out with the pointers and procedures.
Andreas