drivers/twserial: Add protocol driver for "three wire serial" interface.

This pretty unintelligent interface is used on some RTC chips.

Signed-off-by: Detlev Zundel <dzu@denx.de>
diff --git a/drivers/twserial/Makefile b/drivers/twserial/Makefile
new file mode 100644
index 0000000..0b059f3
--- /dev/null
+++ b/drivers/twserial/Makefile
@@ -0,0 +1,46 @@
+#
+# (C) Copyright 2009
+# Detlev Zundel, DENX Software Engineering, dzu@denx.de.
+#
+# See file CREDITS for list of people who contributed to this
+# project.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation; either version 2 of
+# the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+# MA 02111-1307 USA
+#
+
+include $(TOPDIR)/config.mk
+
+LIB	:= $(obj)libtws.a
+
+COBJS-$(CONFIG_SOFT_TWS) += soft_tws.o
+
+COBJS	:= $(COBJS-y)
+SRCS	:= $(COBJS:.o=.c)
+OBJS	:= $(addprefix $(obj),$(COBJS))
+
+all:	$(LIB)
+
+$(LIB):	$(obj).depend $(OBJS)
+	$(AR) $(ARFLAGS) $@ $(OBJS)
+
+#########################################################################
+
+# defines $(obj).depend target
+include $(SRCTREE)/rules.mk
+
+sinclude $(obj).depend
+
+#########################################################################