rtlbt_iov_fetch
hdr = rtlbt_iov_fetch(&iov, sizeof(*hdr));
subsec_hdr = rtlbt_iov_fetch(&iov, sizeof(*subsec_hdr));
subsec_data = rtlbt_iov_fetch(&iov, subsec_len);
hdr = rtlbt_iov_fetch(&iov, sizeof(*hdr));
section = rtlbt_iov_fetch(&iov, sizeof(*section));
section_data = rtlbt_iov_fetch(&iov, section_len);