To design with the more complex parts and the most advanced technologies you really have to climb into bed with the manufacturer. The main reason for this is that designing with parts like this takes a lot of support from the manufacturer which translates into a high cost for them. They want to make sure that you are fully committed to designing with their parts and want to understand fully what your end marketplace potential really is. This in turn allows them to calibrate the value that you represent to them as a customer.
To protect the "break-in" interface with them they often hold detailed specifications close to their chest and only reveal them to committed customers. Often time the first step is contacting their sales organization and/or field applications engineers. You will be asked to sign an NDA (Non Disclosure Agreement) before they will give you access to documentation. This keeps such documentation from getting out into the wild where non-vetted customers would have access to it. In some cases this also gives access to pricing data as fits your customer application and usage volume profile.
To mitigate initial technology evaluation manufacturers will often produce reference boards that you can purchase to "play" with the technology before any NDAs may be necessary. After the documentation is made available it is not uncommon that it will become obvious that the manufacturer will indicate that for the best success that you design your product very closely following the reference design to which they will provide schematics and even full PC board design files. In some cases a very detailed step by step design guide may be provided.
With all of the above said there are still manufacturers that do not privatize the availability of detailed product documentation. (Most FPGA vendors are a good example of this). The trade off for this is that the price for the most high tech parts may be in the 100's of dollars (if not 1000s).
