http://74shkqooxyomdaqa5cfmqaqnxkqp25wsqilpndcik5wbhpds6uqqxeqd.onion/gitlab.freedesktop.org/verdre/iio-sensor-proxy/-/about
For example, the first line of the matrix will define whether
the $ accel~x $ value will correspond to the corrected $ x $, $ y $ or $ z $ axis
(with a $ 1 $ for that axis, and $ 0 $ for the others), or needs to be negated
(by setting it to $ -1 $). A matrix of $ \left[ {\begin{array}{ccc} 0 & 0 & 1\\ 0 & -1 & 0\\ 1 & 0 & 0\\ \end{array} } \right] $ will swap the $ x $ and $ z $ values, and negate the $ y $ reading.