board: samsung: add support for Galaxy A series of 2017 (a5y17lte)

Samsung Galaxy A3, A5, A7 (2017) - middle class Samsung smartphones.
U-boot can be used as chain-loaded bootloader to gain control
on booting vanilla linux(and possibly others) kernels

Signed-off-by: Dzmitry Sankouski <dsankouski@gmail.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
diff --git a/doc/board/index.rst b/doc/board/index.rst
index 1b93ced..74ea33e 100644
--- a/doc/board/index.rst
+++ b/doc/board/index.rst
@@ -23,6 +23,7 @@
    openpiton/index
    qualcomm/index
    rockchip/index
+   samsung/index
    siemens/index
    sifive/index
    sipeed/index