Discoveries by those who have opened up the Nintendo Switch to poke around the hardware, including Tech Insights and Digital Foundry, seem to indicate that the Switch uses a standard Nvidia Tegra X1, as it matches the configuration for the X1.
This conflicts with Nvidia's own claim on their blog prior to the release of the Switch, however, as they claimed that the "Nintendo Switch is powered by the performance of the custom Tegra processor."
It's important to note, though, that there's still a lot of uncertainty as to whether Nvidia meant they were adapting their processor for a dedicated console, or whether the processor has been customised in other ways for the Switch. Either way, its interesting that it matches the Tegra X1 in terms of configuration. How do you think it's customised?