https://www.iar.com/knowledge/learn/programming/using-c-standard-library-time-and-clock-functions/

* bug fixed gpio_mode_set miss gd32_spi->mosi_pin,gd32_spi->sck_pin
* feature,add gd32_spi's alt_func_num member for different spi periph's gpio
* feature,add spi3,spi4,and support multi spi devices
* feature,add rt_hw_spi_device_attach api
* tested on the gd32f450i-eval board

* Decouple the addition of command line arguments

* Decouple the addition of command line arguments

* Modify change logs

* Modify change logs

* Decouple the addition of command line arguments

* delete wrong edits

* Modify file header

* remove duplicate imports

* [bsp] fix gd32vf103_rvstar building issue

* correct descriptions

correct descriptions in ipc.c and timer.c
Co-authored-by: NStanley <stanleylwinn@gmail.com>

[update] Removed C++ global constructor initialization, this method is not used in GCC4.7 and later versions.

* 为spi添加超时检测,避免卡死。提取公共部份，避免代码复制。

* [gcc][armcc][armclang] rtconfig.CROSS_TOOL->rtconfig.PLATFORM

* [stm32f401-nucleo] arduino support
* 增加application arduino main文件
* 调整目录结构

* Microchip SAM MCU BSP update and add ethernet driver

1. Update Microchip SAM MCU BSP, add I2C, GMAC, ADC driver support. 2. Add ethernet driver support of SAM MCU for RT-Thread.

* Add GMAC and I2C driver support

1. Update MCU BSP to support I2C/ADC/GMAC peripherals. 2. Add I2C and ethernet driver and LWIP support. 3. Update serial driver.

* Add I2C driver and move some files to the common folder

1. Add I2C driver. 2. Move the same drivers and demo code to same folder to reduce duplicated code.

* rt1052 添加 RT-Thread Studio 工程

[stm32f072] support Arduino I2C and update readme