Pull rpmsg updates from Bjorn Andersson:
 "Argument validation in public functions, function stubs for
  COMPILE_TEST-ing clients, preparation for exposing rpmsg endponts
  to user space and minor Qualcomm SMD fixes"

* tag 'rpmsg-v4.10' of git://github.com/andersson/remoteproc:
  dt-binding: soc: qcom: smd: Add label property
  rpmsg: qcom_smd: Correct return value for O_NONBLOCK
  rpmsg: Provide function stubs for API
  rpmsg: Handle invalid parameters in public API
  rpmsg: Support drivers without primary endpoint
  rpmsg: Introduce a driver override mechanism
  rpmsg: smd: Reduce restrictions when finding channel

qcom_smd_send() should return -EAGAIN for non-blocking channels with
insufficient space, so that we can propagate this event to user space.

Fixes: 53e2822e56c7 ("rpmsg: Introduce Qualcomm SMD backend")
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

The edge registration functions is to be used from a remoteproc driver
to register and unregister an edge as the remote processor comes and
goes.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

SMD channels are created by the remotes in "opening" state, but
sometimes as we close and try to reopen them they linger in closing
state.

Following the search for a matching channel the create_ept() will verify
that the channel is in a suitable state, so we can lax the restrictions
of the search function to work around above difference in behaviour.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

This introduces a new rpmsg backend for the Qualcomm SMD system,
allowing communication with various remote processors found in Qualcomm
platforms. The implementation is based on, and intends to replace,
drivers/soc/qcom/smd.c with the necessary adaptions for fitting with the
rpmsg core.

Based on original work by Sricharan R <sricharan@codeaurora.org>

Cc: Sricharan R <sricharan@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>