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>

include/tws.h

@@ -0,0 +1,38 @@
+/*
+ * (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
+ *
+ */
+
+#ifndef _TWS_H_
+#define _TWS_H_
+
+/*
+ * Read/Write interface:
+ *   buffer:  Where to read/write the data
+ *   len:     How many bits to read/write
+ *
+ *   Returns: 0 on success, not 0 on failure
+ */
+int tws_read(uchar *buffer, int len);
+int tws_write(uchar *buffer, int len);
+
+#endif	/* _TWS_H_ */