docs/devel/reset: Update to discuss system reset

Now that system reset uses a three-phase-reset, update the reset
documentation to include a section describing how this works.
Include documentation of the current major beartrap in reset, which
is that only devices on the qbus tree will get automatically reset.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20240220160622.114437-11-peter.maydell@linaro.org
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
1 file changed