TPL : introduce the TPL based on the SPL

Due to the nand SPL on some board(e.g. P1022DS)has a size limit, it can
not be more than 4K. So, the SPL cannot initialize the DDR with the SPD
code. This patch introduces TPL to enable a loader stub that is loaded
by the code from the SPL. It initializes the DDR with the SPD or other
operations.

The TPL's size is sizeable, the maximum size is decided by the memory's
size that TPL runs. It initializes the DDR through SPD code, and copys
final uboot image to DDR. So there are three stage uboot images:
	* spl_boot, * tpl_boot, * final uboot image

Signed-off-by: Ying Zhang <b40530@freescale.com>
Acked-by: York Sun <yorksun@freescale.com>
diff --git a/README b/README
index 18f5233..677c3dc 100644
--- a/README
+++ b/README
@@ -3167,6 +3167,17 @@
 		option to re-enable it. This will affect the output of the
 		bootm command when booting a FIT image.
 
+- TPL framework
+		CONFIG_TPL
+		Enable building of TPL globally.
+
+		CONFIG_TPL_PAD_TO
+		Image offset to which the TPL should be padded before appending
+		the TPL payload. By default, this is defined as
+                CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
+                CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
+                payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
+
 Modem Support:
 --------------
 
@@ -4204,6 +4215,11 @@
 		that is executed before the actual U-Boot. E.g. when
 		compiling a NAND SPL.
 
+- CONFIG_TPL_BUILD
+		Modifies the behaviour of start.S  when compiling a loader
+		that is executed after the SPL and before the actual U-Boot.
+		It is loaded by the SPL.
+
 - CONFIG_SYS_MPC85XX_NO_RESETVEC
 		Only for 85xx systems. If this variable is specified, the section
 		.resetvec is not kept and the section .bootpg is placed in the