tty: n_smux: Add SMUX TTY Line Discipline Driver

Add new Serial Multiplexer (SMUX) driver.

This driver multiplexes multiple logical channels over a single
physical HSUART channel using the TTY Line Discipline framework.
This driver will be used in Fusion 4 for control plane, data plane
and DIAG traffic between Application processor and QSC modem.

Change-Id: Ibecf6cea872f5baf11fb93ded6124243a37a2085
Signed-off-by: Eric Holmberg <eholmber@codeaurora.org>
Signed-off-by: Angshuman Sarkar <angshuman@codeaurora.org>
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index bd7cc05..3284647 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -319,6 +319,19 @@
 	  This line discipline provides support for the GSM MUX protocol and
 	  presents the mux as a set of 61 individual tty devices.
 
+config N_SMUX
+	tristate "SMUX line discipline support"
+	depends on NET && SERIAL_MSM_HS
+	help
+	  This line discipline provides support for the Serial MUX protocol
+	  and provides a TTY and kernel API for multiple logical channels.
+
+config N_SMUX_LOOPBACK
+	tristate "SMUX line discipline loopback support"
+	depends on N_SMUX
+	help
+	  Provides loopback and unit testing support for the Serial MUX Protocol.
+
 config TRACE_ROUTER
 	tristate "Trace data router for MIPI P1149.7 cJTAG standard"
 	depends on TRACE_SINK