关于设备框架对接的问题

最近在看设备驱动的代码，以串口举例，我用了3个串口 ，uart1 uart3 uart6。所以uart_obj数组里是3个元素static struct stm32_uart uart_obj[sizeof(uart_config) /sizeof(uart_config[0])] = {0};此时uart_obj里都是 0，代码里也没找到给uart_obj[1].serial赋值的地方，此时uart_obj[1].serial应该也是0，那为什么可以这样呢。

uart_obj[i].serial.ops = &stm32_uart_ops;
uart_obj[i].serial.config = config;
int rt_hw_usart_init(void)
{
rt_size_t obj_num = sizeof(uart_obj) / sizeof(struct stm32_uart);
struct serial_configure config = RT_SERIAL_CONFIG_DEFAULT;
rt_err_t result = 0;
stm32_uart_get_dma_config();
for (int i = 0; i < obj_num; i++)
{
/* init UART object /
uart_obj[i].config = &uart_config[i];
uart_obj[i].serial.ops = &stm32_uart_ops;
uart_obj[i].serial.config = config;
/ register UART device */
result = rt_hw_serial_register(&uart_obj[i].serial, uart_obj[i].config->name,
RT_DEVICE_FLAG_RDWR
| RT_DEVICE_FLAG_INT_RX
| RT_DEVICE_FLAG_INT_TX
| uart_obj[i].uart_dma_flag
, NULL);
RT_ASSERT(result == RT_EOK);
}
return result;
}
问题二：
在rt_hw_serial_register函数里有代码如下：

device->init = rt_serial_init;
device->open = rt_serial_open;
device->close = rt_serial_close;
device->read = rt_serial_read;
device->write = rt_serial_write;
device->control = rt_serial_control;
这样一来，三个串口每个都有这样的操作函数

然后#define ENV_NAME "uart3"
env_dev = rt_device_find(ENV_NAME); 执行这条语句之前，env_dev是0；执行之后env_dev就有了和uart_obj[1]相同的地址。
没搞明白IO设备管理和设备驱动框架层，也就是device 和serial是怎么联系起来的，
比如rt_device_control(env_dev, RT_DEVICE_CTRL_CONFIG, &pconfig);是怎么调用到

static rt_err_t rt_serial_control(struct rt_device *dev,
int cmd,
void *args)
的呢。

我看到rt_hw_serial_register函数里调用ret = rt_device_register(device, name, flag);
再调用rt_object_init(&(dev->parent), RT_Object_Class_Device, name);

rt_device_find 函数里有 return (rt_device_t)rt_object_find(name, RT_Object_Class_Device);
但是没看明白。