 Single- and multi-planar APIs in the Linux Kernel documentation

Primary source: www.kernel.org/doc/html/latest/userspace-api/media/v4l/planar-apis.html

Verified locator: §1.26 defines discontiguous frame sub-buffers and the multi-planar API; §1.26.1 distinguishes multi-planar formats from API usage and states that the multi-planar API can handle single-planar formats. Subsequent subsections identify explicit plane-description structures.