The dpdk documentation indicates that the rte_eal_init takes arguments argc and argv, but there does not appear to be any documentation about options that this function considers valid, or what their meanings are.
The source code lists the options, but doesn't actually explain what each option means.
Is there some place where these options are documented, and their implications for dpdk made clear?
Unfortunately, there is no single place describing all possible options. Some basic options are described in the Getting Started Guide.
The most comprehensive list of EAL command line options could be found in Testpmd User Guide.
For some options, like vdev the description could be found inside the PMD's documentation. For example, here is the description of vdev options for libpcap and ring PMDs.