Hi dav1,
Until now, I didn't see any customer use the HQ camera in the RT. so we still don't have any solutions about 12.3 megapixel Sony IMX477R sensor with RT.
We are mainly using MT9M114 or OV7725 camera module.
Maybe you also can check your Sony IMX477R sensor, whether that can meet the RT CSI demand. About the RT CSI feature, you can check the RT reference manual, CSI chapter.
If you still need help from my side, just kindly let me know.
Best Regards,
Kerry