doc: arch: Convert README.nios2 to reST

Convert plain text documentation to reStructuredText format and add
it to Sphinx TOC tree. No essential content change.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>

doc/arch/index.rst

@@ -9,4 +9,5 @@ Architecture-specific doc
    arm64
    mips
    nds32
+   nios2
    x86

doc/arch/nios2.rst

@@ -1,10 +1,15 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Nios II
+=======
+
 Nios II is a 32-bit embedded-processor architecture designed
 specifically for the Altera family of FPGAs.
 
-Please refer to the link for more information on Nios II,
+Please refer to the link for more information on Nios II:
 https://www.altera.com/products/processors/overview.html
 
-Please refer to the link for Linux port and toolchains,
+Please refer to the link for Linux port and toolchains:
 http://rocketboards.org/foswiki/view/Documentation/NiosIILinuxUserManual
 
 The Nios II port of u-boot is controlled by device tree. Please check
@@ -13,33 +18,38 @@ out doc/README.fdt-control.
 To add a new board/configuration (eg, mysystem) to u-boot, you will need
 three files.
 
-1. The device tree source which describes the hardware, dts file.
+1. The device tree source which describes the hardware, dts file:
-    arch/nios2/dts/mysystem.dts
+   arch/nios2/dts/mysystem.dts
 
-2. Default configuration of Kconfig, defconfig file.
+2. Default configuration of Kconfig, defconfig file:
-    configs/mysystem_defconfig
+   configs/mysystem_defconfig
 
-3. The legacy board header file.
+3. The legacy board header file:
-    include/configs/mysystem.h
+   include/configs/mysystem.h
 
 The device tree source must be generated from your qsys/sopc design
-using the sopc2dts tool. Then modified to fit your configuration. Please
+using the sopc2dts tool. Then modified to fit your configuration.
-find the sopc2dts download and usage at the wiki,
+
+Please find the sopc2dts download and usage at the wiki:
 http://www.alterawiki.com/wiki/Sopc2dts
 
-$ java -jar sopc2dts.jar --force-altr -i mysystem.sopcinfo -o mysystem.dts
+.. code-block:: none
+
+   $ java -jar sopc2dts.jar --force-altr -i mysystem.sopcinfo -o mysystem.dts
 
 You will need to add additional properties to the dts. Please find an
 example at, arch/nios2/dts/10m50_devboard.dts.
 
 1. Add "stdout-path=..." property with your serial path to the chosen
-node, like this,
+   node, like this::
+
 	chosen {
 		stdout-path = &uart_0;
 	};
 
 2. If you use SPI/EPCS or I2C, you will need to add aliases to number
-the sequence of these devices, like this,
+   the sequence of these devices, like this::
+
 	aliases {
 		spi0 = &epcs_controller;
 	};
@@ -47,49 +57,55 @@ the sequence of these devices, like this,
 Next, you will need a default config file. You may start with
 10m50_defconfig, modify the options and save it.
 
-$ make 10m50_defconfig
+.. code-block:: none
-$ make menuconfig
+
-$ make savedefconfig
+   $ make 10m50_defconfig
-$ cp defconfig configs/mysystem_defconfig
+   $ make menuconfig
+   $ make savedefconfig
+   $ cp defconfig configs/mysystem_defconfig
 
 You will need to change the names of board header file and device tree,
 and select the drivers with menuconfig.
 
-Nios II architecture  --->
+.. code-block:: none
-  (mysystem) Board header file
+
-Device Tree Control  --->
+   Nios II architecture  --->
-  (mysystem) Default Device Tree for DT control
+     (mysystem) Board header file
+   Device Tree Control  --->
+     (mysystem) Default Device Tree for DT control
 
 There is a selection of "Provider of DTB for DT control" in the Device
 Tree Control menu.
 
-( ) Separate DTB for DT control, will cat the dtb to end of u-boot
+   * Separate DTB for DT control, will cat the dtb to end of u-boot
-binary, output u-boot-dtb.bin. This should be used for production.
+     binary, output u-boot-dtb.bin. This should be used for production.
-If you use boot copier, like EPCS boot copier, make sure the copier
+     If you use boot copier, like EPCS boot copier, make sure the copier
-copies all the u-boot-dtb.bin, not just u-boot.bin.
+     copies all the u-boot-dtb.bin, not just u-boot.bin.
 
-( ) Embedded DTB for DT control, will include the dtb inside the u-boot
+   * Embedded DTB for DT control, will include the dtb inside the u-boot
-binary. This is handy for development, eg, using gdb or nios2-download.
+     binary. This is handy for development, eg, using gdb or nios2-download.
 
 The last thing, legacy board header file describes those config options
-not covered in Kconfig yet. You may copy it from 10m50_devboard.h.
+not covered in Kconfig yet. You may copy it from 10m50_devboard.h::
 
-$ cp include/configs/10m50_devboard.h include/configs/mysystem.h
+   $ cp include/configs/10m50_devboard.h include/configs/mysystem.h
 
 Please change the SDRAM base and size to match your board. The base
 should be cached virtual address, for Nios II with MMU it is 0xCxxx_xxxx
 to 0xDxxx_xxxx.
 
-#define CONFIG_SYS_SDRAM_BASE		0xc8000000
+.. code-block:: c
-#define CONFIG_SYS_SDRAM_SIZE		0x08000000
+
+   #define CONFIG_SYS_SDRAM_BASE		0xc8000000
+   #define CONFIG_SYS_SDRAM_SIZE		0x08000000
 
 You will need to change the environment variables location and setting,
 too. You may change other configs to fit your board.
 
-After all these changes, you may build and test.
+After all these changes, you may build and test::
 
-$ export CROSS_COMPILE=nios2-elf-  (or nios2-linux-gnu-)
+   $ export CROSS_COMPILE=nios2-elf-  (or nios2-linux-gnu-)
-$ make mysystem_defconfig
+   $ make mysystem_defconfig
-$ make
+   $ make
 
 Enjoy!