This filter was added back in 2017 for QEMU 2.11 but it was never
properly documented, so let's explain how it works and add a couple of
examples.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Message-Id: <20200921173016.27935-1-berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>