Add a KUnit test suite covering __iio_chan_prefix_emit(), the helper that builds IIO sysfs attribute name prefixes from an iio_chan_spec. The suite groups cases by the enum iio_shared_by mode it exercises: - IIO_SHARED_BY_ALL: produces an empty prefix. - IIO_SHARED_BY_DIR: emits direction only ("in" / "out"). - IIO_SHARED_BY_TYPE: emits "<dir>_<type>" and the differential "<dir>_<type>-<type>" variant. - IIO_SEPARATE: covers the full matrix of indexed, differential, modified, output and extend_name combinations, plus the two documented error paths (differential without indexed, differential with modifier). A final case exercises the seq_buf overflow path by passing an undersized buffer and expects -EOVERFLOW. Also, an entry is created under MAINTAINERS dedicated to tests for IIO core helpers. Signed-off-by: Rodrigo Alencar <rodrigo.alencar@analog.com> Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>