Changes

====U-Boot SPL(BELK 4.0.0 or newer, BXELK 2.0.0 or newer)====TBDThese kits use U-Boot SPL as first-stage bootloader. It is loaded by the internal bootrom during the boot process. U-Boot SPL is run to set up the PS and load the second stage bootloader (U-Boot).  U-Boot SPL is built with the same tool chain used to build the the other software modules, such as the Linux kernel and the applications.  Please note that U-Boot SPL is based on one file (<code>ps7_init.c</code>) that is generated by Vivado. In turn, this file contains some initialization parameters that are set according to Zynq configuration. The U-Boot sources provided by the BELK/BXELK include such file. Unless you need to modify the initial Zynq configuration, you don't need to generate a new <code>ps7_init.c</code> file. Therefore, from the standpoint of the software running on PS, Vivado is genrally not required. 

The Linux kernel running on the target needs to mount a root file system. Building a root file system from scratch is definitively a complex task because several well-known directories must be created and populated with a lot of files that must follow some standard rules. Again we will use pre-packaged root file systems that make makes this task much easier. <u>Please note that using a pre-packaged root file system can lead to conflicts with the application binaries obtained using the pre-built cross-toolchain: as a general rule, dynamically linking an application against libraries built with a different toolchain can cause malfunctioning.</u>