Record networking and DMA development progress

Add the current OS source tree, build scripts, system image layout, and development notes covering DMA page allocation, e1000 bring-up, net API dispatch, and DHCP work in progress.

CODE/UTSM/include/utsm/net.h

@@ -0,0 +1,42 @@
+#ifndef UTSM_NET_H
+#define UTSM_NET_H
+
+#include <utsm/types.h>
+
+#define DKM_NET_MAX_DEVICES 8u
+
+/* 网卡链路/能力标志。 */
+#define DKM_NET_F_LINK_UP  (1u << 0)
+#define DKM_NET_F_TX_READY (1u << 1)
+#define DKM_NET_F_RX_READY (1u << 2)
+
+typedef int (*dkm_net_tx_fn)(void *ctx, const void *packet, u32 length);
+typedef int (*dkm_net_rx_poll_fn)(void *ctx, void *buffer, u32 capacity, u32 *out_length);
+
+typedef struct dkm_net_device_desc {
+    const char *name;
+    u8 mac[6];
+    u32 flags;
+    void *ctx;
+    dkm_net_tx_fn tx;
+    dkm_net_rx_poll_fn rx_poll;
+} dkm_net_device_desc;
+
+typedef struct dkm_net_device_info {
+    const char *name;
+    u8 mac[6];
+    u32 flags;
+} dkm_net_device_info;
+
+typedef struct dkm_net_api {
+    int (*register_device)(const dkm_net_device_desc *desc);
+    u32 (*device_count)(void);
+    int (*device_info)(u32 index, dkm_net_device_info *out);
+    int (*tx)(u32 index, const void *packet, u32 length);
+    int (*rx_poll)(u32 index, void *buffer, u32 capacity, u32 *out_length);
+} dkm_net_api;
+
+void net_init(void);
+const dkm_net_api *net_get_api(void);
+
+#endif