Documentation/zh_CN: Add basic LoongArch documentations

Add some basic documentation (zh_CN version) for LoongArch. LoongArch is
a new RISC ISA, which is a bit like MIPS or RISC-V. LoongArch includes a
reduced 32-bit version (LA32R), a standard 32-bit version (LA32S) and a
64-bit version (LA64).
Reviewed-by: Alex Shi <alexs@kernel.org>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Co-developed-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Documentation/translations/zh_CN/index.rst

@@ -171,6 +171,7 @@ TODOList:
    riscv/index
    openrisc/index
    parisc/index
+   loongarch/index
 
 TODOList:
 

Documentation/translations/zh_CN/loongarch/features.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+.. include:: ../disclaimer-zh_CN.rst
+
+:Original: Documentation/loongarch/features.rst
+:Translator: Huacai Chen <chenhuacai@loongson.cn>
+
+.. kernel-feat:: $srctree/Documentation/features loongarch

Documentation/translations/zh_CN/loongarch/index.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+.. include:: ../disclaimer-zh_CN.rst
+
+:Original: Documentation/loongarch/index.rst
+:Translator: Huacai Chen <chenhuacai@loongson.cn>
+
+=================
+LoongArch体系结构
+=================
+
+.. toctree::
+   :maxdepth: 2
+   :numbered:
+
+   introduction
+   irq-chip-model
+
+   features
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`

Documentation/translations/zh_CN/loongarch/irq-chip-model.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+.. include:: ../disclaimer-zh_CN.rst
+
+:Original: Documentation/loongarch/irq-chip-model.rst
+:Translator: Huacai Chen <chenhuacai@loongson.cn>
+
+==================================
+LoongArch的IRQ芯片模型（层级关系）
+==================================
+
+目前，基于LoongArch的处理器（如龙芯3A5000）只能与LS7A芯片组配合工作。LoongArch计算机
+中的中断控制器（即IRQ芯片）包括CPUINTC（CPU Core Interrupt Controller）、LIOINTC（
+Legacy I/O Interrupt Controller）、EIOINTC（Extended I/O Interrupt Controller）、
+HTVECINTC（Hyper-Transport Vector Interrupt Controller）、PCH-PIC（LS7A芯片组的主中
+断控制器）、PCH-LPC（LS7A芯片组的LPC中断控制器）和PCH-MSI（MSI中断控制器）。
+
+CPUINTC是一种CPU内部的每个核本地的中断控制器，LIOINTC/EIOINTC/HTVECINTC是CPU内部的
+全局中断控制器（每个芯片一个，所有核共享），而PCH-PIC/PCH-LPC/PCH-MSI是CPU外部的中
+断控制器（在配套芯片组里面）。这些中断控制器（或者说IRQ芯片）以一种层次树的组织形式
+级联在一起，一共有两种层级关系模型（传统IRQ模型和扩展IRQ模型）。
+
+传统IRQ模型
+===========
+
+在这种模型里面，IPI（Inter-Processor Interrupt）和CPU本地时钟中断直接发送到CPUINTC，
+CPU串口（UARTs）中断发送到LIOINTC，而其他所有设备的中断则分别发送到所连接的PCH-PIC/
+PCH-LPC/PCH-MSI，然后被HTVECINTC统一收集，再发送到LIOINTC，最后到达CPUINTC::
+
+     +-----+     +---------+     +-------+
+     | IPI | --> | CPUINTC | <-- | Timer |
+     +-----+     +---------+     +-------+
+                      ^
+                      |
+                 +---------+     +-------+
+                 | LIOINTC | <-- | UARTs |
+                 +---------+     +-------+
+                      ^
+                      |
+                +-----------+
+                | HTVECINTC |
+                +-----------+
+                 ^         ^
+                 |         |
+           +---------+ +---------+
+           | PCH-PIC | | PCH-MSI |
+           +---------+ +---------+
+             ^     ^           ^
+             |     |           |
+     +---------+ +---------+ +---------+
+     | PCH-LPC | | Devices | | Devices |
+     +---------+ +---------+ +---------+
+          ^
+          |
+     +---------+
+     | Devices |
+     +---------+
+
+扩展IRQ模型
+===========
+
+在这种模型里面，IPI（Inter-Processor Interrupt）和CPU本地时钟中断直接发送到CPUINTC，
+CPU串口（UARTs）中断发送到LIOINTC，而其他所有设备的中断则分别发送到所连接的PCH-PIC/
+PCH-LPC/PCH-MSI，然后被EIOINTC统一收集，再直接到达CPUINTC::
+
+          +-----+     +---------+     +-------+
+          | IPI | --> | CPUINTC | <-- | Timer |
+          +-----+     +---------+     +-------+
+                       ^       ^
+                       |       |
+                +---------+ +---------+     +-------+
+                | EIOINTC | | LIOINTC | <-- | UARTs |
+                +---------+ +---------+     +-------+
+                 ^       ^
+                 |       |
+          +---------+ +---------+
+          | PCH-PIC | | PCH-MSI |
+          +---------+ +---------+
+            ^     ^           ^
+            |     |           |
+    +---------+ +---------+ +---------+
+    | PCH-LPC | | Devices | | Devices |
+    +---------+ +---------+ +---------+
+         ^
+         |
+    +---------+
+    | Devices |
+    +---------+
+
+ACPI相关的定义
+==============
+
+CPUINTC::
+
+  ACPI_MADT_TYPE_CORE_PIC;
+  struct acpi_madt_core_pic;
+  enum acpi_madt_core_pic_version;
+
+LIOINTC::
+
+  ACPI_MADT_TYPE_LIO_PIC;
+  struct acpi_madt_lio_pic;
+  enum acpi_madt_lio_pic_version;
+
+EIOINTC::
+
+  ACPI_MADT_TYPE_EIO_PIC;
+  struct acpi_madt_eio_pic;
+  enum acpi_madt_eio_pic_version;
+
+HTVECINTC::
+
+  ACPI_MADT_TYPE_HT_PIC;
+  struct acpi_madt_ht_pic;
+  enum acpi_madt_ht_pic_version;
+
+PCH-PIC::
+
+  ACPI_MADT_TYPE_BIO_PIC;
+  struct acpi_madt_bio_pic;
+  enum acpi_madt_bio_pic_version;
+
+PCH-MSI::
+
+  ACPI_MADT_TYPE_MSI_PIC;
+  struct acpi_madt_msi_pic;
+  enum acpi_madt_msi_pic_version;
+
+PCH-LPC::
+
+  ACPI_MADT_TYPE_LPC_PIC;
+  struct acpi_madt_lpc_pic;
+  enum acpi_madt_lpc_pic_version;
+
+参考文献
+========
+
+龙芯3A5000的文档：
+
+  https://github.com/loongson/LoongArch-Documentation/releases/latest/download/Loongson-3A5000-usermanual-1.02-CN.pdf (中文版)
+
+  https://github.com/loongson/LoongArch-Documentation/releases/latest/download/Loongson-3A5000-usermanual-1.02-EN.pdf (英文版)
+
+龙芯LS7A芯片组的文档：
+
+  https://github.com/loongson/LoongArch-Documentation/releases/latest/download/Loongson-7A1000-usermanual-2.00-CN.pdf (中文版)
+
+  https://github.com/loongson/LoongArch-Documentation/releases/latest/download/Loongson-7A1000-usermanual-2.00-EN.pdf (英文版)
+
+注：CPUINTC即《龙芯架构参考手册卷一》第7.4节所描述的CSR.ECFG/CSR.ESTAT寄存器及其中断
+控制逻辑；LIOINTC即《龙芯3A5000处理器使用手册》第11.1节所描述的“传统I/O中断”；EIOINTC
+即《龙芯3A5000处理器使用手册》第11.2节所描述的“扩展I/O中断”；HTVECINTC即《龙芯3A5000
+处理器使用手册》第14.3节所描述的“HyperTransport中断”；PCH-PIC/PCH-MSI即《龙芯7A1000桥
+片用户手册》第5章所描述的“中断控制器”；PCH-LPC即《龙芯7A1000桥片用户手册》第24.3节所
+描述的“LPC中断”。