The R41Z can be configured as a network co-processor with NXP’s FSCI (Freescale Serial Communication Interface).
Further documentation for the R41Z / KW41Z FSCI is in the KW41Z Connectivity Software package. The full package is available for Windows & Linux. See the “Protocol Stack” section at this link.
There are a number of documents that are included in with the install. Not all of them are available for direct download from the NXP website.
This link has some additional information. (It mentions the KW40Z, though the concepts are the same.)