[coreboot] How to understand register address on x86?

[김유석]

Dear Sir.

This time, I try to read the "V2_Avoton_BWG_Rev1_6_review.pdf" Page 169. 
Is see below.

But I don't understand the SLOTCAP address (*B0:D1**-**4:F0**:*Offset 
0x54[31:19]).

Could you explain this mean to me?

Thank you.