Your friend and mine, super-hacker Brian Swetland, walks you through the major steps along the way of a five-day journey going from nothing to having a functional NVME driver for Zircon (formerly Fuchsia). There are links to the relevant Gerrit reviews for each stage of the project. As he puts it,

The end results are a (possibly interesting) window into how I go from a zero to functional driver. The first section presents the very first shell of a driver I checked in. Each following section shows the diffs from the version preceeding it to that version of the driver. These focus on nvme.c, the guts of the driver, but nvme-hw.h (the header file with registers and structures and such) and rules.mk (the Zircon build system file) are also present.