Extend the safety overview with information about the IEC 61508 standard
and why it was chosen for zephyr.
Add a new diagram which shows relations between the IEC 61508
and other standards.
Signed-off-by: Simon Hein <Shein@baumer.com>
Add the safety documentation to the Zephyr documentation tree.
Starts with the safety overview which describes the general goals
for the safety in zephyr and introduces a process overview how a safety
certification can be achieved in the zephyr project.
Signed-off-by: Simon Hein <Shein@baumer.com>