What is the best Chinese equivalent for "passion" or "to be passionate about something"?
In your case, passion could be translated into "热情"(zeal),"激情"(deep love), or "爱好"(hobby). Note that "激情" could also mean "passion" as in romantic relationships.

I would like to describe the pattern for this word. In general, you would say "对X的热情/激情/爱好" to mean "passion for X".

And for your example "My passion is rockclimbing", you could say "我的爱好是攀岩", or “我对攀岩富有热情/激情", but I would like to express it in a simple way,


  我酷爱攀岩。 


"酷爱" means "to love something deep" as a verb here.