Interesting AMD patent recently published. No guarantee this is how RDNA will do raytracing but it gives a good idea of how AMD is thinking about it.
https://www.techspot.com/news/80724-amd-patent-describes-hybrid-approach-real-time-ray.html
https://www.techspot.com/news/80724-amd-patent-describes-hybrid-approach-real-time-ray.html