The following documents are available:
The NVDIMM Namespace Specification [pdf] describes a method for sub-dividing persistent memory into namespaces, which are analogous to NVM Express Namespaces. The document also describes the Block Translation Table (BTT) layout which provides single sector write atomicity for block devices built on pmem (see this blog post for more information on the BTT).
The NVDIMM Driver Writers Guide [pdf] is targeted to driver writers for NVDIMMs that adhere to the NFIT tables in the Advanced Configuration and Power Interface (ACPI) V6.0 specification, the Device Specific Method (DSM) specification and the NVDIMM Namespace Specification. This document specifically discusses the block window HW interface and persistent memory interface that Intel is proposing for NVDIMMs. A version of the document with change bars [pdf] from the previous version is also available.
The NVDIMM DSM Interface Example [pdf], Version 1.3, is targeted to writers of BIOS and OS drivers for NVDIMMs whose design adheres to the NFIT Tables in the ACPI specification. The document specifically discusses the NVDIMM Device Specific Method (_DSM) example.