log: Add an implementation of logging

Add the logging header file and implementation with some configuration
options to control it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index c024b41..7cda689 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -310,6 +310,13 @@
 T:	git git://git.denx.de/u-boot-i2c.git
 F:	drivers/i2c/
 
+LOGGING
+M:	Simon Glass <sjg@chromium.org>
+S:	Maintained
+T:	git git://git.denx.de/u-boot.git
+F:	common/log.c
+F:	cmd/log.c
+
 MICROBLAZE
 M:	Michal Simek <monstr@monstr.eu>
 S:	Maintained