add section about booting procedure

user-doc/user-doc.tex

@@ -290,4 +290,23 @@ Then we can write the \path{u-boot.bin}, \path{bzImage} and \path{initramfs.cpio
 ./sunxi-fel -p spiflash-write 0x080000 bzImage
 ./sunxi-fel -p spiflash-write 0x400000 initramfs.cpio.gz
 \end{minted}
+
+\section{Booting ROTS}
+
+After powering up the board, \emph{u-boot} will be loaded.
+\emph{u-boot} will then load the Linux kernel image and the initramfs from the SPI NOR flash and boot the Linux kernel with the initramfs as follows:
+
+\begin{minted}[breaklines]{text}
+sf probe 0:0 6000000
+sf read 42000000 80000 380000
+sf read 43000000 400000 400000
+bootm 0x42000000 0x43000000
+\end{minted}
+
+The ROTS kernel will now boot up and mount the initramfs as the rootfs.
+At some point the kernel will run the init script in the initramfs.
+When this happens the ROTS will start communicating with the TBM to fetch the time as well as the certificates.
+Once these have been retrieved from the TBM, the ROTS will mount the external media such as hard disks and enumerate and verify possible boot images on those media.
+
+
 \end{document}